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

Hobbyists often need to make water changes in order to imitate nature. Because wastes are continually being flushed down the drains, most waterways have low levels of nitrates. Unfortunately for us, the byproduct of feeding our fish is nitrates. When this parameter is kept low, fish will be at their healthiest.

Generally below 40 parts per million is considered safe for most fish. A simple way to regulate this is by changing water. The act of changing water can be as easy as it sounds. We want water without nitrates to be taken out and replaced with water that has them. I’d like to focus on how to regulate the water quality. Hobbyists only change their water every other month. You’ll often hear hobbyists say, “change your water every other month.” But there are also those who insist on changing it every week. Some discus breeders do it every single day. Who is right?

Both are right and wrong at the same moment. They are correct that they have a schedule that works for them. They are all wrong to recommend a particular water change schedule. It is better to show the individual how to assess their water changing requirements. First we need to realize that every tank will have a different water change schedule. This is because each tank will have a different bio-load. The amount of fish combined with how much food is fed is how you determine the bio-load. It’s not hard to understand that more fish will be thrown away if there is more food. Conversely, less fish and food would result in less waste. We need to figure out how much waste we’re producing. Test your water for nitrates to find out how you can measure it.

Your nitrate levels will rise every week when you keep your tank moderately full. Once we can track how our nitrates are rising, we can start to regulate it. As an example, I am going to use an aquarium that produces 10ppm of nitrates per week. As we have stated, we want to keep the nitrates at 40ppm. In this example, we can see that after 4 weeks our aquarium hits 40ppm. We must perform a water change. We conduct a 30% water exchange. This will reduce our nitrates by 30%. Our new nitrate count is 28ppm. Our fish will have 10ppm of the nitrates within a week. Our count will now be at 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. Although larger water changes may seem better, drastic water changes can cause stress to plants and fish. The goal of changing water is to keep the fish healthy. If doing a large water change causes stress and illness, then it’s not completing our goal. You may be thinking, “But I don’t want water changed every week.” Don’t worry, you can tune an aquarium to fit your needs.

You can help combat the need for water changes by feeding less, or simply keeping less fish. There is also the option of getting a larger aquarium. If you have more fish than water volume, the waste will be spread over more water. That means less parts per million. My last recommendation for combating water changes is to add live plants to your aquarium. When they grow, they consume nitrates. Don’t be fooled, even with all the above techniques, tanks still require water changes. It’s only a matter of how long between the water changes.

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