Additives
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| Calcium hydroxide powder, used as an additive to top off water for maintaining calcium and alkalinity levels. |
Introduction
There is a vast array of additives available for a marine tank and it isn't always clear what hobbyists need to use and what they don't need. This is particularly difficult for those new to the hobby who see all these wonderful additives making all the claims under the sun about how wonderful they are for a reef aquarium.
The general rule of thumb for adding anything to a tank is to only add things if you KNOW you need to. What does that mean? Test the water parameters first and then only add something if it is lacking.
Additionally, if you cannot test for it, you should not be adding it! How do you know if you are adding the right amount?
Also see What Parameters to Test.
Definite
Most established marine tanks only require maintenance of calcium and alkalinity. These can be maintained using a separate additive for each (one for calcium, one for alkalinity), but it is generally better to use a combined solution such as kalkwasser. This will add calcium and alkalinity in the same ratios it is used for calcification. One off adjustments of calcium can be performed with calcium chloride (e.g. Damp Rid). One off adjustments of alkalinity can be performed with sodium bicarbonate (baking soda, bicarb soda).
Some tanks suffer from low magnesium and regular dosing of a magnesium supplement may be required (but only after first testing). One off adjustments can be done using magnesium sulphate (Epsom salts). For more regular dosing magnesium chloride should be used if possible to avoid raising sulphate.
May Be
Iodide has been reported as being a required additive, but definitive information of this is currently absent. Only add it if levels are low relative to natural salt water and ensure have a quality test kit to monitors levels.
Similarly, strontium is a popular additive of which its requirement is still highly questionable. It is very similiar to calcium, so if calcium levels are low it is be used by calcifying organisms. However, with suitable calcium levels, it should make no difference as long as it is around ballpark NSW levels.
Resources
- The “How To” Guide to Reef Aquarium Chemistry for Beginners, Part 2: What Chemicals Must be Supplemented by Randy Holmes-Farley - Reefkeeping Magazine
- Inorganic Substances as Additives in the Marine Aquarium by John Linville, instructions on how to make own solutions for addition of calcium, strontium, iodine and bicarbonate - Thiel's InfoBase
- Balling Light Method - for addition of calcium, magnesium and carbonates.
