A Buyer's guide to calcium additives
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.
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.
The way kalkwasser reacts with other chemicals in the water is a little complicated, so the effect it has depends on the initial chemistry of your system. Kalkwasser reacts with CO2 present in the water and adds calcium and bicarbonate ions. If there's plenty of CO2 it produces calcium bicarbonate (which boosts the alkalinity). If there's not enough CO2, or if the pH is too high, some of the calcium precipitates to calcium carbonate, which is less soluble. Over time, this will lead to a drop in alkalinity, which you'll need to counter through the addition of buffers like sodium bicarbonate.
It can be an effective means of maintaining good calcium and alkalinity levels, but some reckon it's much harder to get these to levels beyond those seen in natural sea water, especially if the rate of evaporation is low and the calcium demand is high. There is also some evidence to suggest it causes significant internal differences in coral growth. It can be dodgy in the wrong hands and is really something for the more experienced reefkeeper.
-Calcium chloride additives
Most of the additives on the market are probably based on anhydrous or dihydrate forms of calcium chloride - either as liquids or powders. On its own, calcium chloride pushes up calcium levels, but it can eventually cause a drop in alkalinity that needs to be countered through the addition of buffers. Some products contain little else apart from calcium chloride, while others may be combined with buffers, like sodium chloride, to help boost alkalinity.
Calcium chloride-based additives can be useful in tanks with medium or low calcium demand and are often used in conjunction with other additives, like two-part additives and kalkwasser. Calcium chloride-based additives can alter the chemistry of the water over time, particularly if few partial water changes are made.
Our test results suggest that several of these also contain additional magnesium (no bad thing in itself) - although this isn't always mentioned on the packaging.
-Two part additives
Balanced two-parters, like C-Balance and Kent's Tech CB, or three-parters like ab Aqua Medic's Reef Calcium, are a clever and effective way of maintaining good levels of calcium and alkalinity. They add calcium and alkalinity in balanced ratios without messing up the balance of the water chemistry. So we think these are the safest bet, if a calcium reactor is out of the question.
The individual parts are kept in separate bottles to prevent them from reacting and forming insoluble chemicals. Essentially, when mixed together they form a sort of salt mix with a very high calcium level. They always come in liquid form - if they came as powders moisture in the air would allow the formation of insoluble calcium carbonate.
Some reefkeepers use calcium chloride-based additives to provide an initial boost, or to make minor adjustments, and then maintain those high levels using two-part solutions. Some of these may cause the s.g. of the water to rise a bit, so keep an eye on it. The cost of use may be higher than some calcium chloride supplements, but remember that you're actually dosing more than just calcium, and everything should be properly balanced.
(CONT)
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.
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.
The way kalkwasser reacts with other chemicals in the water is a little complicated, so the effect it has depends on the initial chemistry of your system. Kalkwasser reacts with CO2 present in the water and adds calcium and bicarbonate ions. If there's plenty of CO2 it produces calcium bicarbonate (which boosts the alkalinity). If there's not enough CO2, or if the pH is too high, some of the calcium precipitates to calcium carbonate, which is less soluble. Over time, this will lead to a drop in alkalinity, which you'll need to counter through the addition of buffers like sodium bicarbonate.
It can be an effective means of maintaining good calcium and alkalinity levels, but some reckon it's much harder to get these to levels beyond those seen in natural sea water, especially if the rate of evaporation is low and the calcium demand is high. There is also some evidence to suggest it causes significant internal differences in coral growth. It can be dodgy in the wrong hands and is really something for the more experienced reefkeeper.
-Calcium chloride additives
Most of the additives on the market are probably based on anhydrous or dihydrate forms of calcium chloride - either as liquids or powders. On its own, calcium chloride pushes up calcium levels, but it can eventually cause a drop in alkalinity that needs to be countered through the addition of buffers. Some products contain little else apart from calcium chloride, while others may be combined with buffers, like sodium chloride, to help boost alkalinity.
Calcium chloride-based additives can be useful in tanks with medium or low calcium demand and are often used in conjunction with other additives, like two-part additives and kalkwasser. Calcium chloride-based additives can alter the chemistry of the water over time, particularly if few partial water changes are made.
Our test results suggest that several of these also contain additional magnesium (no bad thing in itself) - although this isn't always mentioned on the packaging.
-Two part additives
Balanced two-parters, like C-Balance and Kent's Tech CB, or three-parters like ab Aqua Medic's Reef Calcium, are a clever and effective way of maintaining good levels of calcium and alkalinity. They add calcium and alkalinity in balanced ratios without messing up the balance of the water chemistry. So we think these are the safest bet, if a calcium reactor is out of the question.
The individual parts are kept in separate bottles to prevent them from reacting and forming insoluble chemicals. Essentially, when mixed together they form a sort of salt mix with a very high calcium level. They always come in liquid form - if they came as powders moisture in the air would allow the formation of insoluble calcium carbonate.
Some reefkeepers use calcium chloride-based additives to provide an initial boost, or to make minor adjustments, and then maintain those high levels using two-part solutions. Some of these may cause the s.g. of the water to rise a bit, so keep an eye on it. The cost of use may be higher than some calcium chloride supplements, but remember that you're actually dosing more than just calcium, and everything should be properly balanced.
(CONT)