Making Your Own Live Rock

[jhnrb]

THOUGHT THIS ARTICLE WOULD BE OF SOME INTEREST FOR THOSE THAT WANTED TO MAKE THEIR OWN REEF ROCK.

By, Tom Miller

Reef Propagation Project:

The Complete Cookbook for Making Live Rock from Cement and Other Types of Rock.

-Includes How to Grow Great Coralline Algae and Make Live Sand-
Have you ever wondered if your hobby could support or pay for all of, or maybe more than all of its own expenses? It certainly would be nice if your hobby could at least pay part of its own way. Or, perhaps you would just like to save a small pile of money on the cost of live rock when setting up your next aquarium? You can do this when you learn how to make your own live rock. It isn't hard at all. People often ask me what types of rock can safely be used for making, growing or culturing their own live rock. The next problem many of them have run into in the past is finding some of the types of rock I've recommended. We're going to answer those questions in detail and solve any problems, right here and now! We're going to look at how to find suitable rocks for in-tank live rock aquaculture and how to go about the actual process of culturing or making them into live rock. I'll tie it up with the results of some very recent additional curing tests of cement rock and how to cure it best so that it is reef-safe.

Lately I have been getting more than the usual number of questions from readers who are having problems with not being able to grow nice looking purple and pink coralline algae on the live rock in their reef tanks. We'll also go over how to cure this missing coralline problem in this month's column.

-Land Based Rocks that can be used to Culture Live Rock.

You can make a lot of your own saltwater aquarium rock or reef aquarium live rock by adding plain whitish-beige aragonite rock, calcite rock or other reef safe rocks to your aquarium. It is a good idea to use ample amounts of rock in reef aquariums, and also in fish-only aquariums. This gives the fish more territory and hiding places. A tank devoid of rock is not as homey to the fish. A good combination of irregular rocky formations with some open space in between is appealing to the observer as well. Coralline algae, other reef life and good bacteria from the existing live rock in your reef tank will slowly spread to the new bare rocks. You can easily grow great looking fully coralline encrusted pieces of live rock in about four to eight months, but occasionally faster. Currently land based rocks that were long ago formed in the ocean are a good choice of rock to use. Some people use rocks like limestone in the form of calcite, or aragonite rocks from old reefs that are now above sea level. The younger it is geologically, the better it is, say perhaps under a million years old. True aragonite is the youngest reef generated rock or sand. Tufa rock also works well and is available at many aquarium stores now. It is a whitish-beige lightweight porous calcium carbonate, magnesium and mineral rock formed on land from geothermal activity. Some people also use landscaping limestone to culture live rock.

Some, but not all, lava rocks work well for live rock culture. Be cautious though, some types of lava rock just leach too many minerals and grow cyanobacteria (red, green and other colored slime algae) and hair algae very readily. If you've seen other people using a particular type of lava successfully without problems, then you're probably safe using the type they are using too.

Some people build the base or main structure for their reef or fish tank from any of the varieties of rock listed above, and then add some nice established cultured live rock or wild live rock or even ocean cultured live rock over parts of it, in many or just a few spots. This live rock from the ocean or from another good reef aquarium provides the "seed" culture for coralline algae, beneficial bacteria, tiny crustaceans (amphipods, decapods and copepods)and other goodies which multiply, spread and grow on and in your new rock also. I have even seeded Idaho aragonite rock with coralline algae in one 20-gallon reef tank with only the coralline on a few snails, hermit crabs and a live sand culture containing some small bits of coralline algae. Of course it took a lot longer to get really good looking live coralline rock with this very conservative seeding method. I prefer to use live rock for the "seed" coralline, NOT live sand with coralline mixed in with it.

I seeded another live rock and live sand growing tank (55-gallon) with only some home grown live sand and two 2-3 inch pieces of heavily corallined live rock. I put the well corallined rocks directly in the heaviest water flow from a power head. This helps spread the coralline algae spores around the tank and to the new rock faster. This grew nice coralline live rock much faster than the previous tank. Faster water motion in the tank (and across the seed rocks) helps here. Two MaxiJet 1000's work well to keep the water moving well in a 55-gallon live sand and live rock growing tank. These two tanks only had single or double flourescent lights of the Triton and Blue Moon Reef types which are 40 watt standard output. Two to four standard output reef tubes over a 45, 50, 55 or 75-gallon tank is ideal lighting for growing a good tank full of coralline live rock. You might as well grow live sand right in with your live rock at the same time. You need to use either enough live sand or live rock in with the new sand and rock to act as a starter culture to spread worms, amphipods, decapods and copepods along with coralline algae, to multiply and populate the new sand and rock. Of course some coral cuttings can be grown on top of all this in the same tank.

If you sell or trade the newly grown coralline live rock that you have just raised, you can then replace it with more dry base rock to keep growing more live rock. You will also have coralline algae growing on the inside glass of the tank by this time. If possible do not remove it, since it also provides seed culture in the form of spores, bits and pieces which can help spread coralline algae to the new rocks even faster the second time around. The more coralline algae on your glass and existing rocks, the faster the new rocks tend to grow coralline. Another trick that helps spread coralline algae is to scrub the coralline on the glass or a rock just a little with an abrasive aquarium cleaning pad or tooth brush to create coralline dust that can be blown around and settle on the new rocks to grow. Good water current is helpful. I do not use filter pads nor do I protein skim the tank during this initial phase, or especially when I scrub the coralline to "seed" the tank with coralline. Filter pads and protein skimming can remove spores or fine coralline dust which I want to encourage in the early stage of getting the rocks to start growing coralline algae.

The only calcium, magnesium or strontium additive I normally use to grow my coralline live rock is CaribSea aragonite sand. The aragonite sand dissolves slowly to provide these while buffering your water just fine on its own. Oolitic aragonite sand from CaribSea or ESV Company can also be used. I normally use no kalkwasser or buffers to culture homegrown live rock. I usually add iodide and a broad spectrum trace element and vitamin supplement such as CombiSan, Reef Plus or Vital Gold twice a week in smaller than recommended doses while growing coralline encrusted live rock. Other trace elements are used by others also. Some aquarists do not even add any other trace elements or iodide other than what the aragonite sand releases as it dissolves.

Using SeaChem's trio of Reef Plus (trace elements and vitamins), Reef Calcium (organic calcium) and Reef complete (calcium, magnesium and strontium) can speed up the process of coralline growth somewhat. Aragonite sand does release calcium, magnesium, strontium and some other elements too. Calcium and magnesium are especially vital to coralline algae growth. Organic calcium accelerates the growth of coralline algae also. Many people have experienced increased coralline algae growth when using Marc Weiss' Coral Vital.

END PART 1 - CONT. PART 2

 

[jhnrb]

Making Live Rock Part 2

CONT. FROM PART 1

Now we come to the two most common causes of poor coralline algae growth. The first cause is low pH and KH (alkalinity). The second common cause of poor coralline growth is the use of excessive herbivores, especially ones that like to eat coralline algae! You can use a supplement like SeaChem's Reef Builder to boost alkalinity and pH a bit and accelerate some cases of slow coralline algae growth. If you decide to use it, I would use smaller conservative doses more often rather than large doses less often. Take the recommended weekly dose and use just 1/4 of that dose twice a week. Others see accelerated coralline algae growth when using balanced calcium/buffer supplements, like ESV's B-Ionic two part calcium supplement. It is also heavy in calcium and magnesium and it raises the alkalinity (KH) of your aquarium water. Be careful not to add too much at any one time.

Some people also see good results by adding kalkwasser, but if you over do this also, you will then get some negative results. If you boost the KH much over 10 - 12 dKH for a long time it could negatively affect your aragonite sand and stop it from readily dissolving to buffer and release calcium. The same precaution applies to using kalkwasser or buffers which can raise the pH and KH too high resulting in precipitation of calcium and magnesium and then aragonite sand failure. More people experience this problem than realize it. I still tend to just stick with the simple aragonite, trace element and iodide combination for a reliable and acceptable coralline algae growth rate.

Using algae eaters such as tangs, snails, amphipods and copepods can be helpful also. You need to keep the hair algae at bay so the coralline algae can take hold and grow. Small blue legged hermit crabs or scarlet hermit crabs are included by some also. Red legged hermit crabs from the Sea of Cortez, although fairly efficient cleaners, like to eat the faster growing types of soft coralline algae and have been totally or partially excluded from some commercial coralline rock growing systems for this reason. I get letters from people who are adding the above supplements to speed the growth of coralline algae and it still doesn't grow! Too often the mystery of the missing coralline turns out to be the use of too many red legged hermit crabs. This results in the rocks ending up with a dull gray-green look which is easy to identify once you've seen it a few times. I can get better coralline algae growth by simply using only CaribSea aragonite sand and no coralline eaters, than the person who uses all the additives above and is hooked on using coralline eaters. Or if you are in a real hurry to grow good coralline algae, you can get the very fastest growth by eliminating the coralline algae eaters and also adding some of the above supplements.

*****(Multible reef aquariums are all dosed with the same top rated additives to provide trace elements, vitamins, calcium, magnesium, strontium, and elevated pH and KH. These are ideal conditions for growing coralline algae! So why isnt the coraline algae growing? Puzzled??? What else do these reef tanks have in common? They each have a good number of Mexican red leg blue spot hermit crabs which not only help clean the tanks of undesirable algae, but also eat coralline algae. The hermit crab Clibanarius digueti from the Mexico area is a coralline algae eater, and is only one of many varieties of hermit crabs called "red leg hermit crabs". Two of the "red leg" hermit crabs from the Sea of Cortez, AKA Gulf of California, have big appetites for coralline algae, C. digueti is the most common one sold.*****

Many sea urchins can eat significant coralline algae also, especially when they get large. Some urchins eat more coralline algae than others. Even common turbo and astrea snails can eat some coralline algae if you have far too many of them and not enough hair algae for them to eat. One of the best hair algae eating snails is the Trochus snail which looks a lot like an astrea but gets only a little bit larger in the aquarium. Gram for gram, Trochus snails seem to be able to clean more and faster than other snails. I have not observed them eating noticeable amounts of coralline algae either. Astrea snails are also good since they are small and don't knock things over like large fast eating turbo snails can.

High phosphates and very high nitrates can slow down coralline algae growth too, but not as bad as the above mentioned corallinavors. If you use phosphate remover excessively, you will also see a slowdown in coralline algae growth since every living thing needs some phosphate to grow. That's why depriving your tank of phosphate can also get rid of hair algae!

Here is a project you might want to try if you are planning to make some extra live rock to sell or trade. You might even take advantage of natural lighting outdoors this summer. You can do this with cement rocks or the other types of rocks as well. Get a simple 5 foot diameter plastic kiddie play pool that is a foot deep for about $10 at Wal-Mart or Toys R Us. Set the pool on a sheet of Styrofoam or old carpet or padding of some kind. Add saltwater and two MaxiJet 1000 or 1200 power heads to circulate the water. Use a heater to make sure the temperature does not drop below about 75 at night. You might have to use a fan set on a timer to come on for several hours each afternoon to cool the water. Don't let the water go above 85 degrees. Use 2 - 4 four inches of CaribSea Reef Sand or Aragamax oolitic sand ( or a mixture) on the bottom of the pool to provide calcium for growing coralline algae on the rocks. You will also be culturing this aragonite sand into live sand while you are growing the live rock. Add your base rocks and a little bit of live sand. Add a few nice coralline algae covered seed rocks in some of the swifter current.

You will also have to cut down the light level since coralline algae bleaches out in full sunlight. You will need to cut the sunlight down by at least 80%! Build a simple square frame with a few intermediate supports using 8 foot long 1x2s and screws. Attach two or even three layers of blue plastic tarp over this frame. This will shade it from direct sunlight down to the point that coralline algae can actually grow and thrive. It will also help keep your live rock growing pool from overheating! Coralline algae also seems to grow best in blue light. For this matter, you might even do well just putting the pool on the shaded north side of a house or building where it just gets blue lighting from the sky, and no direct sunlight. This light level might be low enough, especially if you then cover it with the frame with clear plastic over it instead of the layers of opaque blue plastic tarp.

A few things to watch out for if you do this outdoors this summer. First, make sure your cement rock is fully cured so you don't kill your whole project! Coralline does not grow very fast in cold water. It needs to be over 75 degrees for it to grow more quickly. Around 80 degrees seems to be about optimum in aquariums. Be sure to check evaporation of the water daily since it can evaporate more quickly out doors. During the summer while the live rock is growing, make arrangements of where you will trade it or sell it in the fall. Some store owners might be more open to the idea of trading or especially selling it on consignment since this will save them the up front cost of buying the live rocks and sand from you first. When the time comes, you can use five gallon buckets and Rubbermaid tubs to transfer the rocks and sand to the store or to other buyers.

END PART 2 CONT. PART 3

 

[jhnrb]

Making Live Rock Part 3

CONT. FROM PART 2

-Using Cement to make Live Rock in Creative Shapes.

An excellent alternative is to make cement reef rocks in your own choice of interesting shapes and sizes. Please read and follow the simple, proper and vital pH curing and testing procedures listed below if you make cement reef rocks. Making and using cement rock for aquariums is nothing new. Public aquariums and aquarists in the United States and Europe used cement long ago. Dick Perrin of Tropicorium has used cement in the past for culturing live rock. About a decade ago he started making cement rocks to grow into live rocks for sale. He now uses mostly CaribSea's Reef Rocks when growing aquacultured live rocks. Using cement to make creatively shaped rocks for reef aquariums is a lost art of sorts that is being revived and developed even better and further this time around. This is a fun project for the typical "Home Depot Aquarist"! It takes only a little advance planning and it does take some time and patience, but it is fun, cheap and it works nicely. Yes, it is "cheap fun" too. You do have to take some precautions since cement initially has a very high pH, but the advantages are well worth while. You can make any shape you can imagine or mold. Cement rock also grows coralline algae well. People have used various sands, including aragonite sand and crushed coral, combined with Portland cement (a greyish powder) and water.

According to professor P.K. Mehta's and P. Monteiro's book "Concrete", a typical cement contains these compounds (and their engineering names): calcium oxide, silicon dioxide, aluminum oxide, iron oxide, magnesium oxide, sulfate, water, 3*calcium silicate (three calcium atoms and one silicate) -- Called C3S 2*calcium silicate -- Called C2S. There are other compounds that are combos of the above. For example C3A, C2A...

In general practice, there are 5 types of cement: Type I: For general use, contains all of the five primary compounds. Type II: Better Sulfite resistance and lower heat of hydration. Less C3A and C3S. Type III: Maximum 15% C3A -- (Note: Cures faster, hence higher early strength). Type IV: Low heat of hydration -- Mostly C2S. Type V: Best of the five types for resistance to "Sulfate Attack" (That is corrosion of the re-bar inside of a concrete section) This means that the cement itself is less permeable.

Conclusions as they relate to making cement rocks for reef aquariums: You can use any type of cement powder that is available. Type II or III might be slightly preferable in some ways, but don't worry too much about this unless these are readily available. Use a high enough water/cement ratio to ensure that ALL the Calcium Silicate is hydrated (bound with water). Always use fresh water (not saltwater) to mix concrete. Concrete gains most of its strength in the first seven days of curing. Type III cures much faster and gains high strength early, hence this cement type is also called "high/early" cement. Cure your cement rocks the first two days under a wet burlap sack or with a plastic covering over it, or in an enclosure to prevent fast evaporation and drying. It will gain higher strength if kept moist during this setting-up time.

After this step you can put it in fresh tap water to finish curing and leaching out high pH compounds and silicates. None of the major compounds in HYDRATED (fully cured) cement look particularly harmful to the aquarium according to Wiseman. The cement itself doesn't really corrode or leach away into your aquarium after reasonable curing in water. In fact, some aquarists have cured the two day old rock right in their reef tanks, but ONLY while using CO2 dosing equipment. DO NOT do this unless you have a CO2 dosing system to keep the pH from climbing when curing it in your aquarium. Otherwise you can loose animals from high pH shock if CO2 dosing or proper curing is not used first. Even then, you can still get more silicate leaching into your aquarium than you might care for. This could also lead to aragonite sand clumping as well. When cement/concrete is "curing" it is actually absorbing water molecules - hydrating. After about 28 days it is mostly finished hydrating or curing, but cement actually keeps hydrating VERY slowly indefinitely. As it hydrates it releases calcium oxide and calcium hydroxide which are two forms of kalkwasser. This is the main reason you want to cure your cement in water for at least a month or two so these forms of kalkwasser can leach out and not end up overdosing your aquarium and killing your reef life with high pH. This has happened to some people who get too anxious, or are uninformed.

Being slower and s-Cement Reef Rock Recipes.

Try this good simple basic recipe to make some of the cheapest porous cement reef rock around. It costs only about 9 cents a lb using this recipe! Using a five gallon bucket, add 5 cups of common easy to find type I/II Portland cement from Home Depot, a hardware store or building supply store. Add 25 cups of crushed oyster shell from a farm feed store. Add six cups of water and mix very thoroughly with a small hand held flower gardening digger. Use rubber gloves to protect your hands from chemical burning due to extended exposure to the high pH of the fresh cement - this is like soaking your hands in supersaturated kalkwasser. Tip the bucket on a 45 degree angle and rotate or roll it to help tumble and mix the cement well. Use the gardening hand digger to mix the cement as you tumble it in the bucket. If the mix is too dry add a little more water (slowly). Karen Holt tries for a final mix with the consistency of cottage cheese. Others go a bit wetter than this, but not too slushy. Many sand substitutes can also be used to make your cement if desired. More on this later. You can get crushed oyster shell at the farm feed store since it is used as a very common chicken feed supplement. And that, my friend, is why THIS cement reef rock recipe is so "cheep, cheep, cheep"!

Do not make the final product too runny or you will not be able to shape it into nice looking irregular shapes as well. An almost slushy mixture that will still stand up just a little and take some shape (just a bit) is just right for molding. In fact, James Wiseman advises that a wetter mix not only assures that the silicates in the cement mix get hydrated and bound, but a slightly wetter mix will produce more micro-pores or capillaries throughout the cement for better bacterial colonization inside the rocks. On the other hand, this can also weaken the cement just a bit, but usually not critically so. On the other hand, don't make it too dry or the cement will have too many large airspace gaps between sand or crushed oyster shell bits and it will then be weaker than the mix that is too wet. Maximum hardness is mostly reached after about a month of curing. Now, using rubber gloves, scoop handfuls of it into a bed of dampened sand (or substitute) for molding and shaping your cement into reef rocks.

Beforehand, you need to prepare this waterproof box or container with sand, crushed coral, aragonite sand or crushed oyster shell. Large plastic garbage can lids work well too. Dig irregular and creative shaped molds in the slightly dampened sand. Karen Holt prefers using the crushed oyster shell cement with about a 1:4 ratio of cement to crushed oyster shell, and uses damp crushed oyster shell for the sand molding bed also. She makes some interesting and intricate shapes with the cement that she calls "lace Rock".

Another alternative box for the sand molding bed that I have used is a large shallow Rubbermaid or Sterilite semi-clear plastic "under bed" storage container with a lid. The lid can be used to cover the container to keep the cement rocks from drying out while they set up for two days. I found some of these cheap containers for only $4.50 at Wal-Mart. They are made by Sterilite and are 2' long by 1.5' wide and about six inches deep. Just right for making four larger rocks or eight smaller ones at once.

You can dig irregular holes in the damp sand molding bed to form "molds" for making creative and or artistic concrete rocks. I like to make holes through some rocks and mound up little heaps of cement on them in irregular shapes so that they look more natural. This is a great way to make arches, rocks with caves and long flattish rocks for creating dramatic overhangs and more caves in your reef aquarium. I like to make small cement rocks to place the large flatter rocks on in my reef aquariums. This keeps more of the sand substrate surface exposed in my reef aquariums. You can easily get up to 90% sand exposure this way. In HANDY Reefs with plenums and sand, I sink these hand made cement support or pedestal rocks down to the top screen just over an inch below the top of the sand. In Berlin style reefs with an inch or two of sand, sink these base support rocks or pedestal rocks down into the sand to the bottom of the tank for more solid support of the rocks above.

END PART 3 - CONT. PART 4

 

[jhnrb]

Making Live Rock Part 4

CONT. FROM PART 3

Karen Holt made a beautiful hollow lacy thin cave rock for my wife by burrowing out a deep hole in the sand molding box (she used crushed oyster shell in place of sand). She fills the hole with a layer of cement by dropping or dribbling small clumpy amounts of the cement mixture onto the hollowed out molding bed so that the fresh cement clumps interconnect for the most part, but it isn't just one solid layer. It ends up looking just a little holey and porous. She then fills in over that with barely damp crushed oyster shell to help it keep its shape as the cement sets up. When it sets up for about two days you can use a stick to brush the sand (or oyster shell) out and off of the new rock. The branching rocks that she makes are quite striking also. The shape variations can be numerous and fun to experiment with.

I have used Karen's technique of dribbling cement in layers and also putting sand or crushed oyster shell placed between parts of layers to make rocks with interconnecting caves and tunnels running through them. To do this, dig an irregular bumpy hole in the sand and dribble the first layer, leaving some holes in it. Then fill the holes you left with barely damp crushed oyster shell or sand and also cover up a couple other spots on the cement with thick portions of the damp sand to help create hollows inside the rock you are making. When you put more cement over this heap of sand, you build it upward in layers of cement and separating pockets of sand. Just dribble your next layer of cement mix over that and keep making holes and tunnels with the intermittently placed pockets of damp sand. When it is has set up for two days, use a wire coat hanger or a stick to dig and clean the sand out of the holes and tunnels it has formed in the cement rocks. This can make really fun tunnelled cement reefs rock! Get creative and have fun.

***** IMPORTANT READ THIS!!! *****

You need to cure your cement rock WELL before adding it to your aquarium, or it can easily boost the pH of the aquarium water well up over 9! Since proper curing is the most critical part of cement reef rock making, we'll go over the warnings here first, and then right afterwards we'll cover some curing methods. Improperly cured cement rock which raises your reef aquarium's pH, is not conducive to growing algae, fish, invertebrates or anything! Improperly cured cement rock = death to aquarium. Others and I have lost fish, live rock, live sand, live coral and more by getting too anxious to introduce cement rock into aquariums. 12 hours or even a few days with a vinegar curing process and then a week or two of fresh water curing didn't work with larger rocks. It lowered the pH but not enough and it can weaken the more delicate cement rock shapes somewhat and still not completely cure them or fully lower the pH. When properly curing in fresh water is complete (five weeks or MORE!) it should no longer raise the pH of fresh tap water and is now safe to add to an aquarium in any amount. Before adding your new cement rock to your aquarium, TEST the rock for high pH.

After you think your new cement rocks have cured enough in water, change the curing water again and then let them set with a new change of fresh water covering them for about four days. Do not aerate the water or even keep it moving during this final curing time before testing the pH. After four days of this final soaking in stagnant water, stir the water the cement is in just before you test the pH of the water. If the pH has risen to 8 or higher then continue curing another three days (to complete another week of soaking) before changing the water again, letting it set four more days in the new water, and then testing the pH of the water again. You can aerate the water during curing, but not before testing the pH or you will get a false low pH reading due to the aeration precipitating out the calcium hydroxide and calcium oxide that causes the high pH.

The object is to find out if the cement is still leaching, not to see if you can cover up the signs of this final curing and leaching. More on complete leaching and pH rebound at the end of this article. Once the cement is fully cured, I no longer detect these pH raising compounds or silicate leaching. DON'T use cement rock until you KNOW that it will not raise the pH of your tank to the point of killing things in it. This high pH will also cause binding and severe clumping of an aquarium's aragonite sand substrate. So, no matter how you choose to cure your cement rock, TEST IT for pH before using it in your aquarium. It makes absolutely wonderful reef aquarium rock if it is properly cured first. Save a reef, cure your rock!


*********************************************************
Jake Levi and I spent a few months in the summer of 1997 doing some long distance joint research on curing and lowering the pH of cement reef rocks. This was after we had both lost reef life due to improperly cured cement rocks when following directions that advised 12 hours or more of initial vinegar curing and then a week or two in fresh water to finish curing. Apparently our cement rocks were NOT cured with this short-cut method. We wanted to know how long it really takes to lower the pH of cement reef rocks to make them totally reef-safe. We had experienced no problems in our aquariums when using several small flat cement "cookies" for attaching coral cuttings to, that had been cured in vinegar and then water. We later found that the small amount of rock (usually less than two cups of uncured small cement "cookies" per 50 gallons) is not enough to raise the pH of the vastly larger aquarium volume very much. We have attached many new coral cuttings to these small cookie sized cement rocks.

Initially, when we started comparing notes, we found that we both had the same pH problem with the medium to large cement reef rocks we had been making and couldn't quite figure out why they would not cure quicker as the directions had said they would. We had both had losses from the high pH of cement rocks that we both assumed were cured. We had tried vinegar in different strengths and varying lengths of time, and then into fresh water for a week, or even two, after the vinegar bath. But, no matter which combination we used, no amount of vinegar or water afterwards, seemed to do the trick for these bigger rocks in just one or two weeks. We tried variations on using vinegar or hydrochloric acid to treat the rock with initially, and then soaking it in fresh water.

We found that it takes at least five to six weeks, in just fresh water only, to cure the cement and lower the pH. The average hobbyist has access to buckets, garbage cans and such. That is what we recommend using for curing containers. After all was said and done, we concluded that you can skip the vinegar or acid pre-treatments and just go for the fresh water treatment only. The calcium oxide and calcium hydroxide (forms of kalkwasser) that slowly leach out of the cement rocks, still take time to leach out of the bigger rocks whether you use acid to neutralize it after it leaches out of the rocks or not.

We used buckets and big plastic garbage cans for the bulk of our curing experiments. I covered my cement reef rocks with fresh water and changed the water once or twice a day for a month by putting a garden hose in the bottom of the rock curing garbage cans and trickling it at a rate of one or two water changes per day. If you don't change the water at all, the process of lowering the pH slows down. However, Jake was still successful with changing the water just once a week for 4-5 weeks. He prefers six weeks to be on the safe side, and then still tests for proper pH and gives the rocks a final two or three weeks in saltwater to be really safe before adding large quantities to a reef aquarium. I have even added a power head to a large plastic garbage can full of rock to circulate the water, but this is not absolutely necessary. Dick Perrin uses about a half cup of muriatic or hydrochloric acid in a 55-gallon plastic barrel full of water and half full of cement rocks with an airlift tube made from PVC pipe to aerate and circulate the water as curing takes place. This method still takes time to get the full curing. It does lower the dramatically high initial pH of the curing water and takes the very worst edge off of the pH. This does not provide complete curing or leaching though. I do NOT recommend using acids like this due to the dangers involved, including chlorine fumes!

END PART 4 - CONT. PART 5

 

[jhnrb]

Making Live Rock Part 5

CONT. FROM PART 4

Keep the curing rocks out of reach of pets and children since the curing water initially has a high pH much like liquid drain cleaner mixed with water does. You can test the pH each week and watch as it stays level, and then starts slowly dropping from above 9 down closer to the pH of your tap water by the end of a month, or usually longer. It can take up to two months sometimes to get a truly total cure with a pH in the 7 range. Both Jake and I noticed another thing that happened when the pH finally dropped and curing was near complete. When curing outdoors, even in strong indirect lighting, we noticed brown algae starting to grow on the cement as it becomes cured. This brown algae-like growth, that can also be long and stringy, is actually filamentatious diatom growth. This is a good sign that the pH has dropped enough so that life can now live on these rocks. You will notice another thing if curing in stagnant water without circulation. The top of the water develops a crust of calcium carbonate as the calcium oxide and calcium hydroxide combine with CO2 at the water's surface. This crust gets thinner with each subsequent water change. In summing up our curing tests from last summer, Jake Levi's method of curing cement reef rocks using only weekly water changes seems to be more practical and the least hassle. I like this simpler method better, even if it takes just a bit longer.

Jake also has a unique recipe for cement rock which he affectionately calls "Rock-a- Roni". Yes, he actually uses pasta in the mix! He adds full pieces of dry ziti to the cement mix and molds the rocks with the many pieces in them. This creates long tunnels through the rocks for better colonization of bacteria and micro fauna. He keeps the proportion of ziti down to 1/5 of the cement volume. More ziti makes the mix crumbly. He cures the Rock-a-Roni extra long to dissolve the pasta out of the cement. He uses a hose with sprayer to wash out the soft ziti after about a month of soaking. It makes a very nice porous cement reef rock. Another variation or special touch he sometimes adds to some of his cement reef rocks is pasta shells. He presses various sized pasta shells into the surface of freshly formed wet cement rocks. They come off easily after the cement sets up and leave interesting and unique shell impressions.

Go make a batch and have fun! There are other variations that some people use. We'll look at them now. Don't be afraid to try some variations and get creative. Just be sure to cure it well, then test the pH before using it in your aquarium. Here are some other sands or rock products that some people use in their cement for live rock. We already mentioned crushed oyster shell which makes a more porous and much cheaper rock than some other options. You can also use crushed coral of any brand or even crushed dolomite from your fish store, used for aquarium substrate, or dolomite from your garden center used as a soil additive. Oolitic aragonite sand from CaribSea or ESV Company also works well. Bob Stark of ESV has had great success with oolitic aragonite cement and also crushed oyster shell cement for several years.

Some people are nervous about using crushed oyster shell which is cheap but higher in phosphate and silicate, which does not leach perceptibly into your tank after proper curing. It has not in mine. Others are still worried about some sources of dolomite, but it has been used successfully. Even white #20 pure quartz silica sand from the hardware store has been used, not only for making cement but for reef aquarium sand substrates too. While this silica sand may look fine and work fine as a substrate, it adds no calcium and does not buffer your aquarium water like aragonite sand substrates do. It does not seem to leach any perceivable silicate into your aquarium either. I do NOT recommend using ordinary sand or gravel used for common cement mixes or pre-mixed dry bagged "post mix". Ordinary gravel and rocks may have higher levels of metals in them, or other substances that you don't want in your saltwater aquarium. The point here is to use sand, rock or gravel that is reef-safe.

-Variations for Making Cement Reef Rocks.

Some people have a real problem finding type II or type III Portland cement that has often been recommended. If you really want to use it, call around to the cement or masonry suppliers in your area. Karen Holt has also used the much more expensive and harder to find pure white Riverside cement with a lot of her rock making. Type III cement is used in cold weather and for cement work exposed to saltwater. In my area I have a hard time getting it until about the first frost in autumn. Type II may be the best of these two cement types. But, regular type I or type I/II Portland cement will harden very well after about a month and are just super and very usable for making cement rocks. Type I/II Portland cement is the most common and can be found at almost any lumber yard, hardware store or home improvement center. Many people have used it very successfully. I now usually just use type I/II and have had good success with it and I highly recommend it.

Type I/II Portland cement normally comes in 94 lb bags for around $5 at Home Depot. I have even used Portland cement powder to make the molds for forming my cement rocks. I still like wet crushed oyster shell or even finer aragonite sand for making molds. Another option is to mix finer aragonite sand with Aruba Shell aragonite from CaribSea for a very nice effect. I usually just use the crushed oyster shell for the sand molding bed now. It is the cheapest and works very well also. Others and I have varied the preferred formula for mixing cement reef rocks and have still had very good success.

Another neat variation on making rocks from cement was sent to me by Paul Baldassano. He has always used Sackrete mortar mix to bond rocks together. He sent a picture of a recent conglomeration rock that he made using many pieces of old coral skeletons and rocks cemented together into a very nice looking irregular arch about a foot and a half long. He used about 3 cups of ready mix Sackrete mortar mix to bond the rocks and coral skeletons together into one final rock sculpture. The sculpture is then allowed to set up for two days, and then it is put in fresh water to cure like regular cement rocks.

What do you do with those spare small pieces of coral rock? Use cement mortar mix to conglomerate them into one big rock sculture for your aquarium. Paul Baldassano has been doing this since the 1970's!

END PART 5 - CONT. PART 6

 

[jhnrb]

Making Live Rock Part 6

CONT. FROM PART 5

Here are two more variations for making cement rocks. I sometimes use a cement to crushed oyster shell ratio of 1:4 or even 1:3 rather than my general recipe above using 1:5. This makes thick or less porous cement mixes for making stronger delicate rock structures with lots of interconnecting caves and tunnels. This extra cement fills in some of the air gaps between the crushed oyster shell bits. When using the general 1:5 recipe above, the rocks are just a bit weaker, but they are so porous that you can run water right through them! This is great for growing tiny rock dwelling critters and good bacteria.

Another way to make very strong cement rocks may or may not be practical for some of you, but here it is for the fearless, anyway. James Wiseman pointed out that Gerwick Company also uses a special additive called silica fume with their cement mix that they use for reef repair in the ocean. It does two things. It can make a cement that hardens to a strength rating of over 10,000 PSI! It also lowers the pH of the cement somewhat. I still recommend curing it just as long for reef aquarium use since it still leaches a lower amount for just as long as regular cement. Silica fume is a very light grey-white powder and is nowadays used to strengthen the cement used for high strength structures that must hold up extra well and extra long and/or be more freeze damage resistant. I only use silica fume when making the delicate structured rocks with lots of tunneling in them. Otherwise I want an overall more porous rock with the regular recipe of 1:5 or maybe even 1:4 cement to oyster shell ratio.

Silica fume can not be found at Home Depot or hardware stores. You can get silica fume from cement additive supply houses or from some cement ready-mix plants. If you really want to try some, then call around to find it. It is rather expensive at $15 to $25 for a 25 lb bag! It is NOT a must-use item. One bag will be much more than the average aquarist will ever use. If however, you are going to make a whole lot of cement rocks, then this will raise your total cost of cement rocks from about 9 cents per lb to about 11 or 12 cents per lb. There are five - 5 lb bags of the silica fume powder in each 25 lb bag. It goes a long way since you only use 5% replacement by weight of the Portland cement. You only use one 5 lb bag per each 94 lb bag of Portland cement! It is twice as light weight as Portland cement so you end up replacing about 8- 9% (by volume) of the Portland cement with the silica fume. James Wiseman cautions that you should not use more than about this 5% amount by weight or you may get additional silicate leaching even after the cement has cured. I use 4 and 1/2 cups of Type I/II Portland cement with 1/2 cup of silica fume powder. This 10% silica fume by volume which is 5% by weight. I mix this with 20 to 25 cups of crushed oyster shell and then I add water and mix it well until it is the consistency of cottage cheese - about five to seven cups. Depending on the desired porosity of the final cement that I want, I use more or less oyster shell. More crushed oyster shell leaves more small air gaps between oyster shell chips. This porousity technique seems to work best with oyster shell. I can slowly run tapwater right through a finished porous rock like this. But, using way too much oyster shell will weeken the cemnet with too many air spaces.

-Results of latest cement curing tests:

In the last couple of months I've been doing additional multitudes of tests and experiments on making cement reef rocks and especially on how best to cure them. I've also been digging up even more info sources in these areas too. I've found that it is best to cure your cement rocks in fresh and not saltwater - initially at least. Curing in saltwater from the beginning can weaken the cement to some degree. You can finish off your curing with saltwater though, and not experience any noticeable weakening. Acid or vinegar curing also weakens - probably much worse than saltwater curing can. Don't use acid or vinegar curing. Save your vinegar for salads. I like apple cider vinegar best since it adds that special tang to my homemade salad dressings! If you want to speed up curing a little bit, it is much better to do so by strongly bubbling or aerating the curing water. This should be as good as using more water changes to speed up the process a little, as I'll explain here shortly. Very cold icy curing water during outdoor winter curing really slows down the process too.

Too much silica fume weakens the rocks a lot. Don't use over 5% (by weight) or you might end up with too much silicate leaching which you will get anyway until the rocks are cured. I tested 5%, 10% and 20% silica fume cement mixes in hopes that the higher percentages would be lower in pH and maybe not even need curing! Not so! The 20% ones were noticeably fragile and breakable. The pH of the stagnant fresh curing water was only very slightly lower when curing cement rocks made with the 10% or 20% silica fume mixes rather than with the 5% mix. I later found that you actually CAN load a tank with brand new 5% silica fume rocks and keep the pH from going too high simply by providing excellent aeration, but I wouldn't anyway. You will still get a lot of silicate leaching with this in-tank curing (with or without silica fume) as it cures. It still has a high pH creating potential (9'ish as opposed to 11'ish) and still must cure even though the pH is lower. Also, if you don't provide high enough levels of aeration, the pH will still go up and hurt things in your aquarium - don't try this in your tank for both of these reasons!

I'm sticking with the out-of-tank fresh water curing whether using low volumes of cement rock or whether using silica fume or not. Curing and subsequent pH leaching is still variable depending on the Portland cement you use and the water amount you mix it with and your tap water and so on. Small thin rocks cure more quickly or at least the pH drops to acceptable levels more quickly, but a full curing still takes time. I can cure a small rock or two right in my aquarium in about two weeks, but you still don't want to do this.

I also noticed what I call a saltwater "pH rebound" when I put cement rocks in saltwater that were cured in fresh water first. This pH rebound is mild, so you may never even notice it. If you cure your cement rocks in fresh water as instructed until the pH is fully lowered, and then transfer them (like normal) to a reef tank you probably won't notice any of this pH rebound since aeration in the reef tank masks this mild pH rebound. Why does aeration hide this pH rebound? CO2 introduced to your aquarium from aeration in modest amounts combines with the released calcium oxide and calcium hydroxide (the two forms of kalkwasser) to make calcium carbonate which can buffer your aquarium slightly. It raises the KH, which you can watch happen in your aquarium with a test kit! On the other hand, if you want to see this pH rebound in action then put the fresh water cured cement rocks in a bucket of stagnant saltwater. You will then be able to monitor the pH as it slowly climbs to about 8.6 or higher within a few days. If you then simply add an open ended air line to aerate this same curing bucket with saltwater and freshwater cured cement rocks, the pH drops rather quickly again while the KH goes up just a little as a result of introducing enough CO2 from the air to create calcium carbonate from the calcium hydroxide and calcium oxide released by the cement. Even with this slight pH leaching rebound when you transfer the freshwater cured cement rocks into you reef aquarium, I have not seen noticeable silicate leaching at this point. You just want to make sure that your aquarium has adequate aeration when you add any cement rock, even when it seems fully cured. It would be a good extra precaution to make sure your tank is very well aerated when you add the cured rocks to it. Use good water surface movement and use your protein skimmer. You could also use a supplemental air stone in the tank.

While still curing the cement rocks in freshwater you can also drop the pH of the curing water with strong bubbling/aeration, but amazingly the KH also tends to go down with the drop in pH in fresh water. After intensely aerating a bucket of curing cement rocks in fresh water for a few days, it is uncommon for the KH to remain above 3 or 4 dKH. This appears to be because the calcium carbonate seems to precipitate out of solution faster in fresh water. It precipitates as a whitish powdery dust on the bottom of the container. This has happened much more readily when curing in freshwater. If you just let the curing water sit stagnant as I often do, then just a few days after you start curing your new cement rocks in stagnant freshwater, the pH may climb to as high as 11 or 12. A reading of 20 dKH is also common while curing in stagnant fresh water. The pH drops on a curve with subsequent water changes, with the most leaching occurring earlier and the last of the curing Seems to drag on a bit.

Now that you have some information on making your own live rock etc. have fun and let us know how you do.

END OF ARTICLE.