This is one of the most commonly asked questions by fish tank owners. Even if the water in your aquarium looks clear enough, a surprising amount of debris will have built up that needs cleaning. You only need to disturb the substrate layer of your fish tank slightly to get an indicator of how much debris has accumulated.
This detritus comes from various sources. One of the biggest contributors is fish food. Even if your fish have healthy appetites, some food particles escape them and fall to bottom of your tank. These particles then decay.
The food that is eaten by your fish is eventually digested and released back into the water as faecal matter and urine, which also compromises water quality. Although some of this debris remains tied up within the gravel layer of your aquarium, much of it is released back into the water as dissolved phosphate and nitrate.
The Impact of Phosphate and Nitrate
Accumulated debris in your aquarium isn’t just unsightly, it also puts the health of your fish at risk. When aquarium water contains high enough levels of phosphate and nitrate, the stress it can put on fish can lead to disease and, in certain cases, death.
Nitrate is particularly harmful to young fish, so if you’re breeding fish species in your aquarium, you should definitely keep an eye on levels of this chemical. Both phosphate and nitrate will also contribute toward excessive algae growth, serving as a fertilising agent for it. The easiest way to avoid all of these issues is to ensure you are changing the water in your fish tank on a regular basis.
How Regularly Should You Change Fish Tank Water?
Frequent water changes are the backbone of aquarium water maintenance. However, various factors will determine how regularly you need to be changing the water within your tank. Larger tanks or those with a high number of fish will need more frequent water changes than smaller, more sparsely populated tanks, for example.
One thing to remember when maintaining your aquarium is that you should never replace the water entirely. Instead, you should be aiming to replace a proportion of the water within your tank. Aim to swap out around 15 percent of the water in your tank once a week.
If your tank is on the large side or if it houses a considerable amount of fish, you may need to replace around 25 percent of the water on a weekly basis. If your tank only houses a handful of fish, water changes can be less frequent. In some cases, you may only need to replace a portion of the water once every month.