under gravel filter

[psness]

I have had incredibly high nitrates for a long time and nothing will drop them (water changes, filter changes, nitrate remover, Chemi-Pure, Purigen). Clerk at the local fish store said it could be due to my undergravel filter, and I shouldn't even have one. I have an underground filter along with a large Eheim cannister filter. I am thinking of replacing my 20-g high with a 25-g tank and am wondering if I should skip the undergravel filter and just use a small bed of sand rather than the shells/crushed coral substrate. I am old school and have a hard time thinking of having a tank without an undergravel filter to aerate the substrate.

 

[marcah]

to me you have a few things causing the issue.. Crushed coral cannister and the undergravel filter.. With your new setup ditch the undergravel and the crushed coral and get aragonite sand for the bottom, the filter can be used to clean any problems you may come across putting charcoal or anything else needed to help the problem but dont put the floss in it.. Just use a media bag filled with what you are using then discard the charcoal or whatever when done...

 

[wontonflip]

+1 Marcha

 

[Zissou]

Everything that Marcah said, and start using RO/DI water if you're not already.

 

[psness]

I've been reading about Plenum filtration that allows anaerobic bacteria to be established deeper in the substrate. Would I essentially accomplish this by just turning off the undergravel filter in my established aquarium? Would this reduce nitrate levels.

 

[Northstar24]

I've been reading about Plenum filtration that allows anaerobic bacteria to be established deeper in the substrate. Would I essentially accomplish this by just turning off the undergravel filter in my established aquarium? Would this reduce nitrate levels.

Its possible, but on a tank of such a small volume, I would not mess around with this type of filtration setup - this is similar to a DSB. The problem with DSB's is if they ever get disturbed, you release sulfuric gas into the water, which has the potential of killing livestock

In a 25 gallon tank, you should be fine with good live rock and a protein skimmer for filtration (along with water changes of course) I would also get rid of crushed coral and get some aragonite sand. To keep the sand clean, look into nassarius snails, hermits, and possibly a sand sifting goby of some sort - they will provide all the sand bed aeration that you need

 

[little_fish]

+1 Everyone

All that stuff is freshwater technology that doesnt translate very well to saltwater, like you have seen with the water quality issues.

 

[Zissou]

I've been reading about Plenum filtration that allows anaerobic bacteria to be established deeper in the substrate. Would I essentially accomplish this by just turning off the undergravel filter in my established aquarium? Would this reduce nitrate levels.

Do you have any fish in your tank, or any inverts?

If it were my tank, I would:

Drain 5 to 10 gallons worth of water and put them into two buckets, and put your livestock in them. Drain as much water as possible and put them into other buckets, and put your rock into those. You should now have a tank with 'disturbed' substrate and polluted water.

Remove the crushed coral subtstrate.

Remove the undergravel filter.

Clean up what you can, then place your wet rocks back into place, then fill on all sides of rock with 1" to 2" of aragonite DRY sand, that's been rinsed thoroughly beforehand.

Put in 5 to 10 gallons of newly made saltwater, pour in slowly. Then fill the rest of the space with old water and livestock. Turn on everything, sit back and wait.

It's a pain, but it's better for the tank in the long run. Just don't remove the rocks or disturb the sand UNTIL the animals are out of the tank, and when most of the water is out of the tank. This way you don't waste what water you have, and don't pollute your rock with any gas or ammonia being released from the old substrate and filter.

Like I stated in another thread, there's nothing in a saltwater tank that really takes up excess nitrates, unless you have a refugium. All an undergravel filter will do is pull in waste and give it a place to rot. Since there are typically no plants, this excess nitrate needs to be pulled out through water changes each week.

 

[Bifferwine]

Undergravel filters are no good for saltwater. They will create nitrate problems. Ditch the UGF, ditch the crushed coral, and go with a shallow sand bed instead. The only thing you need to aerate the substrate are some nassarius snails.

 

[psness]

Zissou and Bifferwine, Your suggestion is what I'm planning on - but also intend on replacing my 20g high tank with a 25g for a little more vertical volume and more room for additional live rock. I have a clown and blue damsel, along with a coral banded shrimp, pacific long-tenticle anemone, pencil urchin, large snail, umbrella coral and a few small groups of zooanthids. I've had success with all my critters, but with high nitrates (and too much green algae) I've always been afraid to get less hardy critters for the tank. Also, out of nowhere, a tiny bunch of fern caulerpa started growing a few weeks ago, which I like and haven't had to prune back yet.

So with the nassarius snails, the sand doesn't require any maintenance? Also, I would like to somehow use at least one of my uplift tube power heads to create some current, in addition to the current created by the spray bar from the cannister filter.

 

[Bifferwine]

I think you are thinking of your tank too much as a freshwater tank. Forget everything you know about aquarium equipment -- the setup you need for saltwater is completely different. If you try to use freshwater techniques and equipment, your tank will not do well.

Here is a good article to start with:
https://www.livingreefs.com/basic-equipment-list-t19611.html

I'm not sure what this uplift tube thing is, can you post a picture? I can tell you that whatever it is, it is not meant for saltwater; neither is a spray bar, and except in rare circumstances (like a fish only tank with no inverts) neither is a canister filter.

You do not need to do anything with the sand if you have sand-stirrers in your clean up crew (nassarius snails). Some people will take a wooden spoon or paint stirrer and gently move a cup or two of the sand around each time they do a water change, but that is not necessary if you keep the sand bed shallow (less than an inch). For a small tank like yours, a shallow sand bed is the way to go.

 

[psness]

Also, I assume it would be a good time to install a protein skimmer.

 

[Bifferwine]

You don't need a protein skimmer on a 20 gallon tank. They benefit you get from them on small tanks is minimal, and most people find it easier just to keep up with regular water changes (10 to 20% a week -- if your nitrates are high, you may want to do more to begin with just to get them to come down initially).

Also, this is just my point of view, but with a small tank you are limited for space. Having a ton of equipment hanging off the back and sides is ugly and cluttered. The less equipment you can use on a tank that size, the better it will look!

How often are you changing your water? And are you using tap water?

 

[psness]

I kept a saltwater tank for about 20 yrs from the early 80's to the early 00's until two years ago when I started back up again, so my thoughts on filtration are evidently old school. I have always had success with an u/g filter and large cannister filter, but can't drop the nitrates over the past two years. The uplift tube is from the u/g filter, which there are two with power heads at the top of each. They help create a lot of current in the tank.

 

[psness]

Your comments about a protein skimmer are why I've not bought one yet, glad to hear your opinion on their usefulness in small tanks. I change 20%-40% once a month...don't say it... I know it would be better to make smaller changes more frequently. Yes I use tap water.

 

[psness]

So how many nassarius snails do I need for a 25 g tank (24"x12" footprint) with 1" to 2" of sand?