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. Most waterways have very low nitrates in the water because wastes are constantly being flushed downstream. Unfortunately, nitrates is the side effect of feeding fish. Fish will be healthier if this parameter is maintained at a low level.

For most fish, a concentration of less than 40 parts per million is safe. This can be easily controlled by changing the water. The act of changing water is as simple 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. Most hobbyists simply change water at a specific interval. You will hear it often: “Change your water every month.” There are some guys who swear to change their water every week. You can also find discus breeders that do it every day! Who is right?

They are all right and all wrong at the same time. They are correct in that the schedule they use works for them. However, they are wrong in recommending a specific water change schedule. A better method is to teach the person how to evaluate their water changing needs. We must first realize that each tank has a unique water changing schedule. Each tank will have a unique bio-load. The amount of fish combined with how much food is fed is how you determine the bio-load. It doesn’t take much thought to realize that more fish combined with more food will result in more fish waste. Conversely, less fish and food would result in less waste. We need to figure out how much waste we’re producing. 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. 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. We want to keep nitrates under 40ppm, as we stated previously. In this example, we can see that after 4 weeks our aquarium hits 40ppm. We must perform a water change. We do a 30% water change. This will decrease our nitrates 30%. Our new nitrate count is 28ppm. We know that our fish will produce 10ppm of Nitrates in a week. Our count will now be at 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. Larger water changes seem like they would be better, however, you can bring on a lot of stress to fish and plants with drastic water changes. 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 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. Be careful not to fool yourself, most tanks will still need water changes even if you use all these techniques. It doesn’t matter how often you wait between water changes.

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