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

We hobbyists need to perform water changes often in order to mimic 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. This parameter should be kept at a minimum to ensure fish are healthy.

Generally below 40 parts per million is considered safe for most fish. This can be easily controlled by changing the water. It is easy to change water. We want to remove water with nitrates and replace it by water that doesn’t. I would like to concentrate on water quality regulation. Hobbyists only change their water every other month. Often times you’ll hear, “change your water every month.” Then there are those guys who say to do it every week. Some discus breeders do it every single day. Who is right?

They can be both right and wrong simultaneously. They are right in that, the schedule they are using 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 must realize that each tank will have its own water change schedule. Because each tank has a different bioload, this is important. The bio-load is determined by the amount of fish and food consumed. It doesn’t take much thought to realize that more fish combined with more food will result in more fish waste. A decrease in fish and food would mean less waste. It is important to determine how much waste we produce. You can do this by checking your water for nitrates.

You will be able to see how your nitrates rise each week if you have a well-stocked tank. We can regulate nitrate levels once we know how they are rising. As an example, I am going to use an aquarium that produces 10ppm of nitrates per week. As stated earlier, we want to keep nitrates below 40ppm. In this example, we can see that after 4 weeks our aquarium hits 40ppm. We will need to do a water changing. We perform a 30% water change. This will decrease our nitrates 30%. Our new nitrate count is 28ppm. Our fish will have 10ppm of the nitrates within a week. Bringing our count back up to 38ppm. As you can see, we will be changing our water every week in line with current trends.

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. Changes in water are intended to help fish stay healthy. If doing a large water change causes stress and illness, then it’s not completing 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. When you add more water volume to the same amount of fish, you’ll spread the waste out over more water, resulting in fewer parts per million. My last recommendation for combating water changes is to add live plants to your aquarium. They eat nitrates as they grow. Do not fool yourself. Most tanks will still require water changes, regardless of how many techniques you use. It doesn’t matter how often you wait between water changes.

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