A guide to calcium additives (PART-1)
MATT CLARKE takes a look at some of the calcium additives on the market.
Calcium is essential to the growth of coralline algae and most invertebrates, especially corals. It is taken up rapidly during growth and needs to be replenished regularly. It's just one of a group of water parameters, including alkalinity, magnesium and salinity, that need monitoring closely if you keep inverts, and it's important that the levels are maintained at a concentration similar to that of natural sea water. In the case of calcium, that's somewhere around the 400 - 420ppm mark. If the levels of these minerals drop too low, it may have a detrimental effect on coral growth and health.
In many cases, newly mixed salt water doesn't even come close to these levels and it's often necessary to replenish the mineral levels. The chemistry of newly mixed salt water varies according to the type of salt you use, and the mineral content of the freshwater you mix with it. Some salts on the market are designed for use with hard, alkaline tapwater and if they're used in conjunction with RO water, the water produced will be lacking in certain important chemicals, especially calcium and magnesium.
There are several salts on the market designed for use with RO water that contain additional minerals to compensate for the low mineral content of the water. In many cases, the salt water produced closely resembles sea water, and in some the calcium and magnesium levels exceed those found in salt water - something seen as beneficial by most modern reefkeepers, some of who now aim for calcium levels of 450 - 480ppm. We tested salt mixes in the September 2001 issue and found that Kent Marine, Instant Ocean and Reef Crystals produced the best water when mixed with RO. ( SOME SALTS AVAILABLE TODAY MAY NOT HAVE BEEN PART OF THE TEST)
-Supply and demand
How much calcium you need to supply depends on the calcium demand of your system. If you've got lots of calcareous algae on your live rock, as well as clams and hard corals, demand is going to be fairly high. You can get a rough idea of how much is being used by measuring how much it drops each day or week.
In some large systems containing significant coral growth, demand could hit 30ppm per day, although it's usually a lot lower than that.
Calcareous substrates, like coral sand, crushed coral, cockle shells and dolomite aren't much good for boosting calcium levels, pH and alkalinity because they don't dissolve until the pH drops below 7.6. Aragonite is better, because it dissolves at pH 8.2, but it's often not enough to do the job on its own and is only really likely to help maintain stable levels.
For systems with low calcium demand, frequent water changes with a mineral-rich salt mix could be enough to maintain the levels seen in natural sea water.
If demand is higher, or you are aiming for calcium, alkalinity and magnesium levels beyond those seen in natural sea water, you will need to supplement these minerals. There are a number of ways to do this:
-Reactors
Calcium reactors are now widely regarded as the best option, because they'll control the calcium, magnesium and alkalinity and add trace elements in a balanced fashion. These units generally sit below the aquarium alongside the sump and need to be fed by a small water pump and supplied with carbon dioxide (CO2) gas from a pressurized bottle.
By passing water slowly through the aragonite-filled reactor, and using CO2 to lower the pH, it's possible to dissolve the aragonite more quickly - allowing it to release lots of minerals into the water. When running properly, these reactors give superb results. They are also much safer than some other forms of control and have fewer negative effects upon overall water chemistry.
Their only real drawback is financial - once you've bought the gas, regulator, hoses and reactor you're looking at a bill of at least a couple of hundred pounds, plus some running costs. However, as our calculations prove, it may actually be more sensible to invest in a reactor than to use additives if you have a large tank or a high calcium demand.
-Additives
For many people, especially newcomers to reefkeeping, additives seem to be the easy option. They're often simple to add, and many are relatively cheap to buy for small systems.
There are dozens on the market, many of which are based around different concentrations of the same basic chemicals. If you can't afford to buy a reactor, they're probably the next best bet. However, many of them can cause imbalances in the chemistry of your water with long-term use. Some produce excess sodium or chloride which can affect salinity, for example, and it's easy to throw alkalinity and calcium levels out of balance with some additives.
There are several different groups of supplement, each based on slightly different chemicals, and each giving a slightly different overall chemical change. It's not always clear what you're getting though. Some manufacturers don't let on exactly what's in their products, or tell you the concentration they provide, or the sort of increase in calcium you can expect from dosing a specific amount...
The additives on the market for replenishing and maintaining calcium levels fall into three main categories:
-Kalkwasser
Kalkwasser, or limewater, is a highly caustic liquid additive made by adding powdered calcium hydroxide (Ca(OH)2) to fresh water, usually RO. After mixing, the clear part of the solution is added very slowly to the aquarium to replace evaporational losses. When done correctly, this can raise the calcium and alkalinity level. When done incorrectly, it can cause violent pH increases and a drop in alkalinity. Special gadgets are available to aid both mixing and addition, which make it much easier to dose than it used to be.
(CONT. PART-2)
MATT CLARKE takes a look at some of the calcium additives on the market.
Calcium is essential to the growth of coralline algae and most invertebrates, especially corals. It is taken up rapidly during growth and needs to be replenished regularly. It's just one of a group of water parameters, including alkalinity, magnesium and salinity, that need monitoring closely if you keep inverts, and it's important that the levels are maintained at a concentration similar to that of natural sea water. In the case of calcium, that's somewhere around the 400 - 420ppm mark. If the levels of these minerals drop too low, it may have a detrimental effect on coral growth and health.
In many cases, newly mixed salt water doesn't even come close to these levels and it's often necessary to replenish the mineral levels. The chemistry of newly mixed salt water varies according to the type of salt you use, and the mineral content of the freshwater you mix with it. Some salts on the market are designed for use with hard, alkaline tapwater and if they're used in conjunction with RO water, the water produced will be lacking in certain important chemicals, especially calcium and magnesium.
There are several salts on the market designed for use with RO water that contain additional minerals to compensate for the low mineral content of the water. In many cases, the salt water produced closely resembles sea water, and in some the calcium and magnesium levels exceed those found in salt water - something seen as beneficial by most modern reefkeepers, some of who now aim for calcium levels of 450 - 480ppm. We tested salt mixes in the September 2001 issue and found that Kent Marine, Instant Ocean and Reef Crystals produced the best water when mixed with RO. ( SOME SALTS AVAILABLE TODAY MAY NOT HAVE BEEN PART OF THE TEST)
-Supply and demand
How much calcium you need to supply depends on the calcium demand of your system. If you've got lots of calcareous algae on your live rock, as well as clams and hard corals, demand is going to be fairly high. You can get a rough idea of how much is being used by measuring how much it drops each day or week.
In some large systems containing significant coral growth, demand could hit 30ppm per day, although it's usually a lot lower than that.
Calcareous substrates, like coral sand, crushed coral, cockle shells and dolomite aren't much good for boosting calcium levels, pH and alkalinity because they don't dissolve until the pH drops below 7.6. Aragonite is better, because it dissolves at pH 8.2, but it's often not enough to do the job on its own and is only really likely to help maintain stable levels.
For systems with low calcium demand, frequent water changes with a mineral-rich salt mix could be enough to maintain the levels seen in natural sea water.
If demand is higher, or you are aiming for calcium, alkalinity and magnesium levels beyond those seen in natural sea water, you will need to supplement these minerals. There are a number of ways to do this:
-Reactors
Calcium reactors are now widely regarded as the best option, because they'll control the calcium, magnesium and alkalinity and add trace elements in a balanced fashion. These units generally sit below the aquarium alongside the sump and need to be fed by a small water pump and supplied with carbon dioxide (CO2) gas from a pressurized bottle.
By passing water slowly through the aragonite-filled reactor, and using CO2 to lower the pH, it's possible to dissolve the aragonite more quickly - allowing it to release lots of minerals into the water. When running properly, these reactors give superb results. They are also much safer than some other forms of control and have fewer negative effects upon overall water chemistry.
Their only real drawback is financial - once you've bought the gas, regulator, hoses and reactor you're looking at a bill of at least a couple of hundred pounds, plus some running costs. However, as our calculations prove, it may actually be more sensible to invest in a reactor than to use additives if you have a large tank or a high calcium demand.
-Additives
For many people, especially newcomers to reefkeeping, additives seem to be the easy option. They're often simple to add, and many are relatively cheap to buy for small systems.
There are dozens on the market, many of which are based around different concentrations of the same basic chemicals. If you can't afford to buy a reactor, they're probably the next best bet. However, many of them can cause imbalances in the chemistry of your water with long-term use. Some produce excess sodium or chloride which can affect salinity, for example, and it's easy to throw alkalinity and calcium levels out of balance with some additives.
There are several different groups of supplement, each based on slightly different chemicals, and each giving a slightly different overall chemical change. It's not always clear what you're getting though. Some manufacturers don't let on exactly what's in their products, or tell you the concentration they provide, or the sort of increase in calcium you can expect from dosing a specific amount...
The additives on the market for replenishing and maintaining calcium levels fall into three main categories:
-Kalkwasser
Kalkwasser, or limewater, is a highly caustic liquid additive made by adding powdered calcium hydroxide (Ca(OH)2) to fresh water, usually RO. After mixing, the clear part of the solution is added very slowly to the aquarium to replace evaporational losses. When done correctly, this can raise the calcium and alkalinity level. When done incorrectly, it can cause violent pH increases and a drop in alkalinity. Special gadgets are available to aid both mixing and addition, which make it much easier to dose than it used to be.
(CONT. PART-2)