Aquarium Water

The most important ingredient in any aquarium is water, and the quality of water used is vital to the health of the freshwater tropical fish.  In the wild, fish live in natural water, which is usually soft, unless they live near chalk which will make the water hard.

The water we use is tap water, which is great for human consumption, but not so good for fish to live in.  Before tap water is put in an aquarium it should be left to stand for a couple of days, and if possible subjected to strong aeration to remove the chlorine from the water.  Alternatively aquarium stockists sell dechlorinating agents which are generally in liquid form, and can be just added to the tap water in the correct dosage, and this will achieve the same result.

Water drawn through copper piping can be toxic to fish, especially if the pipework or storage tank is new, so the first batch of water that flows through the tap, which may have been in the system for a while should not be used.

Normally there is not too much to worry about, as any fish that you buy locally will be used to the local water, but do be careful if you buy from another area, or by mail, as the water could be quite different.

The pH scale

The pH scale is a logarithm measurement denoting the strength of acidity or alkalinity.  The range goes from 0-14, with 0 being strongest acidity, and 14 being strongest alkalinity, and 7 being neutral.  For the aquarist, the pH scale is only relevant between 6.5 and 8.2.  A sample of water can be tested very easily using an inexpensive test kit. 

The pH of water may be relevant if you are considering breeding fish that need absolute ideal conditions in order to do so, but for most aquarists who keep a home aquarium it is not relevant.  Most fish that are bought are bred commercially in water that doesn’t generally correspond to that of their natural habitat, and then moved to the water available at the dealer.

Water Hardness

Probably a better known property of water, hardness, is also an important factor in the fishes comfort and general well-being.  Hardness is due to dissolved salts, usually calcium and magnesium, and it can be temporary or permanent.  Temporary hardness can be removed by boiling the water, but permanent hardness can only be reduced by chemical means or by distillation.  A quick way to reduce hardness is to dilute the water with soft water, and rainwater is ideal for this.

The water hardness will depend on where you live, water pumped from mountainous areas will generally be soft, whereas if it comes from chalk soil it will be hard.

A newcomer should not be daunted by this, as many home aquariums are kept successfully by people who have no knowledge of this.  A simple way to ensure a healthy aquarium is to undertake partial water changes, changing 25% of the water every 4 weeks, and ensuring the water is dechlorinated and the same temperature and quality of the water that was removed.


Just Tropical Fish is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to You will not pay any more, and it helps support our site.