• Marine water

    Life in your aquarium is dependent on the correct saltwater. For that reason you must prepare things properly.

Initial water (Osmosis water)

When filling the aquarium for the first time – and subsequently when partially changing the water – you will need a sufficient amount of water. You can use tap-water but it must be cleaned by reverse osmosis (see Annex: Reverse Osmosis, page 9) and not contain any hazardous residues.

It is particularly important that the nitrate content is minimal (max. 10 mg/l), and that there should be no phosphate (max. 0,1 mg/l), heavy metal (copper, zinc) or silica acid present. Pesticides and medication residues must also be eliminated. These are best removed by activated carbon filtration.

For analysing water there are test kits available from aquarium dealers – and for specific cleaning functions, suitable filtration media from EHEIM.


Nowadays, various kinds of sea-salt are available in the aquarium trade: “standard salt” (not to be confused with table salt!) and various “special salts”, but for beginners, experts recommend “standard salt”. It should be a reliable brand which contains all the important minerals and/or trace elements and it is best to buy it in a sealed bucket so that it does not attract moisture during storage.

For a tropical coral-reef aquarium the salt content should be between 34 and 35.7g per litre. You should ideally weigh out the quantity (e.g. 35 g/l) and pour it slowly into the start up water (not the other way round) and mix thoroughly.

Then (after 24 hours) you must heat the water up to 25 °C, measure the density and adjust salt content.  


Water container
When you fill the aquarium for the first time you can mix the water in the aquarium. When doing partial water changes this is not possible.

Ideally you should put the water in a large container (bath, bucket or similar). Obviously the container must be clean and must not give off any harmful chemicals. A (very clean) plastic bucket can be used for filling.