• The marine water

    Composition of your water

Osmotic water

The initial water will be tap-water. This is cleaned by a process of reverse osmosis (see Annex: Reverse osmosis page 11) to give “ultra-pure water” or “revers osmosis water”. Please test it again. There should be no dangerous residues left (nitrate max. 10 mg/l, phosphate max. 0.1 mg/l), no heavy metals, silicic acids, pesticides or medication residues.

Salt content
The salt content must be between 34 and 35.7g per litre. (Density measured at 25 °C = 1.021 – 1.023 g/ml = 33 – 35.7 g/l).

Water temperature
The temperature must be between 24 and 26 °C. No more and no less as any deviation may jeopardise the ecosystem

Trace elements
Nowadays a good brand of sea-salt will contain up to 70 main and trace elements. If you partially change your water and feed your fish on a regular basis, a second dose will not usually be necessary.
If, after vigorous skimming, the animals have stopped growing and the colours have faded, you can carefully add a second dose using a commercially available solution. But take care – never exceed the amounts specified by the manufacturer because many substances are highly toxic and fatal in larger amounts.

pH value
The pH value indicates whether the water is acid (below 7) or alkali (above 7). It should be between 7.8 and 8.5 and will often be lower in the morning than in the evening because, during the day, in the light, algae absorbs carbon dioxide (CO2) and oxygen is formed. Consumption of acid increases the pH value.
If the pH value is incorrect, a partial change of water will often help. Otherwise the carbonate hardness must be tested and if necessary adjusted.

Carbonate hardness
Carbonate hardness should be 7 – 10° KH. This means acids will be neutralised and fluctuations in pH value impeded to a certain degree (buffering capacity).
If the KH is too low you can obtain a KH-enhancing agent from your specialist aquarium dealer. Acid-forming substances must also be removed from the aquarium (metabolic waste as the result of having too many fish, decaying waste in the substrate etc.). The addition of calcium can also help. Excessive KH will not usually occur unless you have over compensated when trying to increase the values. You will then have to change a greater proportion of the water.

Natural marine water has a calcium concentration of 400 – 450 mg/l. If it drops below 400 mg/l you should add a suitable calcium preparation. If there are hard corals to be nurtured, it is essential that you install a calcium reactor.

Magnesium is important for the formation of calcium. The natural figure for magnesium is about 1350 mg/l but a shortage of magnesium may cause a breakdown in the growth of calcareous algae, allowing thread algae to flourish. With suitable preparations you can administer a second dose.

Nitrite, nitrate, phosphate
These substances are generated by excreta (ammonium/ammonia), dead organisms, decomposition products, food remnants etc. These are largely removed from the water by the protein skimmer and, after a short period, values which exhibit a slight increase will often stabilise. Cleanness and regular, partially water changes will help but in an emergency, specialised filter media (e.g. EHEIM phosphate out) or specialised preparations should be used. You should seek the advice of your specialist aquarium dealer regarding this.




Testing the water
Your specialist aquarium dealer will have everything you need to measure water values. It is essential that you make sure the water test is suitable for marinewater.   

Partial change of water
The most important way of maintaining the water values in your aquarium is by partially changing the water on a regular basis (10 % at least every 14 days).