Calcium alone cannot form the skeletal material of corals and allow calcareous algae to grow. Some other substances are needed as well. A few other constituents are carbonate and bicarbonate. These two substances also have a major impact on the stabilization of the pH in the proper range of 8.1 – 8.4. Such stabilization is also called buffering.
The total carbonate and bicarbonate concentration is also called carbonate alkalinity or carbonate hardness. The only difference between alkalinity and carbonate hardness is a conversion factor.
NSW has an alkalinity of approx. 2.7 meq/L or approx. 7.5 dKH when expressed as carbonate hardness.
For a stable system the alkalinity or carbonate hardness should have a value similar to NSW or slightly higher and should preferably not fluctuate by more than 5%. This means a maximum fluctuation of 0.14 meq/L or 0.4 dKH.
Therefore an alkalinity test kit should be capable in measuring in steps smaller than 0.14 meq/L.
Ammonia and ammonium are substances which should be converted rapidly into nitrite followed by nitrate and nitrogen gas.
If this does not happen then the aquarium is not fully cycled or biological processes are not proceeding as they should.
The Salifert Ammonia test is very straightforward and measures the sum of toxic ammonia and ammonium in just a few minutes.
The kit can perform approx. 50 measurements and can detect 0.5 ppm of total ammonia easily.
Calcium is a major constituent of calcareous algae, skeletal material of hard corals and the skeletal needles of soft/leather corals. Calcium also fulfills many biological functions.
Quite often a too low calcium concentration retards coral and calcareous algae growth.
NSW contains 400 – 450 mg/L calcium. Which is also the value we should strive for. For a stable aquarium environment the fluctuation in calcium content should preferably not more than approx. 15 mg/L. This automatically means that the calcium test should be able to monitor comparable fluctuations.
Iodine is present in NSW (Natural seawater) in a very low concentration (0.06 mg/L or 0.06 ppm).
Iodine occurs as different species. Some of them are iodide, iodate and hypoiodite.
Generally when we say iodine then we mean one or more iodine species without a clear distinction being made. NSW contains predominantly iodate and to a slight extent iodide.
There is however a misconception among many hobbyists that iodide predominates in NSW. This is however false.
Magnesium is present in NSW in a fairly high concentration (1300 – 1400 mg/L). Magnesium is an essential part of
When an aquarium has insufficient regions deprived of oxygen (= anaerobic zones) or denitrification proceeds incompletely then nitrate will build-up.
A too high nitrate concentration can result in unwanted algae-growth and these might irritate corals in their neighborhood.
Nitrate as such also retards coral growth.
The nitrate concentration in a proper functioning reef aquarium should preferably be lower than 1 mg/L. Fish-only aquariums would usually show much higher nitrate concentrations.
Most test kits use a procedure in which a certain part of nitrate is converted chemically into nitrite and is measured as such.
Once again, just as with nitrite testing, amine interference has a major impact on the measured value. If such an interference occurs concentrations much lower than actual will be measured.
Nitrite is a substance that is toxic to fish and invertebrates.
It is a misconception that once a tank is through its cycle (first 3 or 4 weeks) that nitrite has vanished.
Many nitrite test kits suffer from interference by amines (such as naturally occurring and essential amino acids) resulting in a too low measured value especially if the nitrite concentration is relatively low.
Nitrite is converted to nitrate in properly cycled aquariums. The thus formed nitrate is transformed into harmless nitrogen gas (=denitrification). This happens in areas deprived of oxygen within live rock and miscellaneous filter materials.
Before it can be transformed to nitrogen gas the nitrate is first converted back to nitrite. When for whatever reason this particular cycle can not be completed, toxic nitrite can be present in significant concentration and readily be detected by test kits that do not suffer from amine interference.
Oxygen is highly essential for all life forms. Especially corals and marine fish require oxygen concentrations at saturation level. This is because of the low solubility of oxygen in saline water which is approx. 5 – 7 ppm.
The oxygen test measures oxygen concentration in just a few minutes.
Approx. 50 tests per kit. Range: 2- 14 ppm.
The pH value can have a major impact on the growth of corals and calcareous algae and on many biological processes. The pH should not be allowed to fluctuate more than approx. 0.3 units during 24 hours and should preferably be kept between 8.0 and 8.2.
If the pH is too low then the cause may be a too low alkalinity and/or insufficient aeration.
A low pH can be corrected by improving aeration and by increasing the alkalinity to NSW (Natural seawater) value or upto approx 25% above NSW levels.
Phosphate has several negative effects if present in a too high concentration. First of all undesirable algae growth might result. Making an aquarium an unpleasant sight.
Phosphate also blocks or retards the growth of corals and calcareous algae.
One of the scientific studies shows that a phosphate concentration higher than 0.05 mg/L decreases the growth of calcareous algae by 90%!
Washing fish food, which is a rich source for phosphates in a sieve after thawing reduces the input of phosphate tremendously. Also avoiding use of phosphate-rich low-grade activated carbon helps keep phosphate levels as low as possible. Checking the activated carbon for phosphate prior to use is therefore highly recommended.
Silicate occurs especially in tap water or in purified water when the RO or DI unit is not functioning properly. Silicate not only results in diatom bloom but might also block some essential trace elements such as vanadium and molybdenum.
Salifert offers a very sensitive and accurate silicate test kit. Silicate content can be decreased by using the granular Phosphate-Killer or the liquid Phosphate-Eliminator. Although both are designed for phosphate removal they have also a very high affinity for silicate.
Approx. 60 tests per kit. The range is 0.03 – 30 ppm as SiO2.
Strontium plays an important role by accelerating coral and calcareous algae growth.
NSW contains approx. 7 – 9 mg/L strontium.
Since the growth of corals and calcareous algae goes hand in hand with strontium and calcium depletion, depletion of calcium usually means depletion of strontium as well.
It is advisable to maintain a strontium concentration between 5 and 20 mg/L.