How Often Do You Have to Change Water in a Fish Tank?

To mimic nature, we as hobbyists many times, need to do water changes. Many waterways have low levels in nitrates because of the constant flushing of wastes downstream. Unfortunately, nitrates are the result of feeding fish. If this parameter is low, fish will be in their best health.

Most fish are safe when the level is below 40 parts/million. It is easy to control this by changing your water. It is easy to change water. We want to get rid of water that contains nitrates, and make it safe for our children. I would like to concentrate on water quality regulation. Many hobbyists just change their water once a month. You will hear it often: “Change your water every month.” There are some guys who swear to change their water every week. There are also those weird discus breeders who do it every day! Who is right here?

They are all right and all wrong at the same time. They are right in that, the schedule they are using works for them. However, they are wrong in recommending a specific water change schedule. The best way to educate the individual is to show them how to assess their water changes needs. First we need to realize that every tank will have a different water change schedule. Because each tank has a unique bioload, this is important. The bio-load is determined by the amount of fish and food consumed. It’s not hard to understand that more fish will be thrown away if there is more food. In the opposite direction, less food and fish would lead to less waste. It is important to determine how much waste we produce. Test your water for nitrates to find out how you can measure it.

Your nitrates will rise every week when you have a large enough tank. When we track the rise in nitrates, we can adjust our tank. As an example, I am going to use an aquarium that produces 10ppm of nitrates per week. As mentioned earlier, we want nitrates to be below 40ppm. In this example, we can see that after 4 weeks our aquarium hits 40ppm. We need to perform a water change. We perform a 30% water change. This will reduce our nitrates by 30%. Our new nitrate number is 28ppm. We know that our fish will produce 10ppm of Nitrates in a week. This brings our total to 38ppm. We can see here that with the current trends, we’ll be doing a water change every week.

I prefer to perform a 30% water change on my aquariums when it is time. While larger water changes might seem to be more beneficial, it can also cause stress to the fish and plants. Changes in water are intended to help fish stay healthy. If a large water change results in stress or illness, it is not meeting our goal. You might be thinking, but I don’t want to change water every week. Don’t worry, you can tune an aquarium to fit your needs.

By feeding less or keeping fewer fish, you can reduce the frequency of water changes. There is also the option of getting a larger aquarium. You can increase the water volume for the same number of fish. This will spread the waste over more water. The result is a lower parts per million. My last recommendation for combating water changes is to add live plants to your aquarium. They ingest nitrates as they grow. Do not fool yourself. Most tanks will still require water changes, regardless of how many techniques you use. It really is a matter of time between water changes.

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