Tap water has been specially treated to make it safe and clean for human consumption.

Some of the additives in tap water, such as Chlorine, can be toxic to an aquarium.


Tap water needs to be de-chlorinated before being used in an aquarium. If tap water containing chlorine is added to an aquarium the essential bacteria which keeps the fish alive may be killed. Bacteria will not live in water containing chlorine. Without bacteria in the filter system the fish will not survive.

Always use a de-chlorinator such as Stress Coat, Ammo Lock, Aqua Safe or Fresh Start before adding tap water to an aquarium.


Partial water changes help improve fish growth and breeding, help prevent against disease outbreaks, allow potentially lethal pollutants to be removed and also gives the opportunity to cleanse the bottom of the aquarium by using a gravel syphon to perform the water change.


  • Aquariums: Try to replace 20% of the aquarium water every 2 to 3 weeks.
  • BiOrb & biUbe etc : Try to replace 20% of the aquarium water every 4 to 8 weeks.


Remove water from the aquarium using a gravel syphon which will allow the gravel to be cleaned whilst also conducting a water change. Gravel syphons are easy to use and cheap to buy (£4 to £8 depending on size).


Do not remove more than 25% of the water, only in extreme circumstances should more than this be removed.


The removed water needs to be replaced, and the new water should have been prepared for a few hours before the water change commenced. The new water MUST have the same pH value as the aquarium water. Tap water varies in its pH value depending on the type of reservoir or supply used to store & transport the water. The pH of tap water can vary from 5.0 to 9.0, and these changes can occur over a very short period (morning the pH may be 6.5, and only a few hours later it may have changed to 8.6). Therefore ALWAYS test the pH of tap water before using it. If the pH of the new water differs from the aquarium water, use a pH buffer to change the pH value of the new water. This is easy to achieve and quick to carry out.


The other important test to conduct is the temperature of the new water, this should be within 2 deg C of the aquarium water, if possible the temperature should be exactly the same as the aquarium water.


Before the new water can be used it needs to be de-chlorinated. Again this is quick and easy to achieve using a de-chlorinator such as either 'Stress Coat', ‘Ammo Lock', ’Aqua Safe' or ‘Fresh Start' etc. Once this is done, the new water can be added to the aquarium. This must be done slowly to avoid shocking the fish and disturbing the filter.



Urmston Aquatics