How to maintain good water quality in your fish tank

If you are new to fishkeeping, the first thing you should know is that water quality is one of the most important aspects of fishkeeping; it has a direct impact on the health of your fish.

To help you keep your fishes’ water in pristine condition, we’ve put together some key things to remember and some helpful pointers.


Maintain the filter

The filter is the most crucial piece of kit in your fish tank. It helps to reduce the amount of waste in your fish tank and is home to your tank’s ‘biological filter’. The ‘biological filter’ consists of friendly bacteria which ensure the removal of harmful ammonia and nitrite, and converts them into nitrate.

Nitrate is less harmful to fish but should still be removed through regular water changes.

It is important to check the filter is working periodically. You should also clean the filter sponges on a regular basis; do this by filling a separate bowl with a small amount of tank water and gently rinsing them. You should never use tap water to clean your filter sponges – tap water contains chlorine and/or chloramines which will damage the biological filter.

Filter sponges will also need replacing every so often, but try not to replace all of the filter sponges at the same time. This will remove a lot of friendly bacteria from your fish tank, and can compromise the water quality going forward.

Conduct regular water changes and treatment

As mentioned above, nitrate can be removed from your fish tank through regular water changes; we recommended doing a partial water change every two weeks. The percentage will vary depending on your tank size and the number of fish, but we suggest changing around 25% of the water each time. A good tip is to use a gravel cleaner when removing water as you’ll also remove a lot of solid waste from the bottom of your aquarium.

Before adding fresh tap water to your fish tank make sure you treat it with King British De-Chlorinator to remove the chlorine and/or chloramines.

On a weekly basis, add King British Filter Aid+. This adds friendly bacteria to your fish tank which helps maintain the ‘biological filter’, and helps to reduce harmful ammonia and nitrite from the water.

Test the water and check the conditions

To maintain the correct conditions for your fish, you should test the water quality regularly, as well as checking the temperature and, if keeping tropical fish, the heater.

King British 6 in 1 Test Strips test for ammonia, nitrite, nitrate, general water hardness, carbonate hardness and pH, and come with a leaflet explaining how to combat different water quality problems.

Testing the water is a great time to check on your tank conditions as well. Different species of fish require different water conditions to thrive. If your tank doesn’t meet their requirements this could cause your fish stress, which can lead to health problems.

If you’re finding it hard to keep the water temperature at the ideal point, consider your tank position. Sunlight can quickly heat up your tank beyond the temperature at which your fish can cope, and also encourages excess algae growth.

If you’re keeping tropical fish, the heater is extremely important and should be checked on a daily basis. It’s a good idea to have a spare aquatic heater on hand just in case you discover your current one isn’t functioning correctly.

Don't overfeed your fish

If you overfeed your fish, any uneaten food remains in the fish tank and will begin to decompose. As the food decomposes it releases additional harmful ammonia into the water. This places a greater burden on the filter, which may mean it can’t work as effectively.

To avoid this, only feed your fish enough food to last for 2 minutes per feed, and remove any uneaten food after this time.

Other things to consider

Tank size

It’s common for first time fishkeepers in particular to choose a small fish tank thinking it will be easier to maintain. Actually, when it comes to water quality it is much easier to maintain good water quality in a larger tank.

In larger tanks, changes in water quality are less concentrated and can be tolerated better by your fish and more easily remedied by you than in a smaller fish tank, allowing more acceptance for error.

If you’re finding you’re having a hard time maintaining the water quality, consider whether you have space for a larger fish tank. You can always visit your aquatic shop for advice. Just remember that water changes, filtering and tank cleaning will take up relatively more time in a larger tank.

Ornaments and Substrates

Double check that the substratebstrate and fish tank ornaments are suitable as some can increase or decrease pH levels. Remember that when you add new ornaments, they may introduce contaminants to your tank. It’s a good idea to give them a clean before adding them. You can do this in the same way you would clean a filter sponge.

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