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

Hobbyists often need to make water changes in order to imitate nature. Many waterways have very low levels of nitrates because wastewater is constantly being flushed downstream. Unfortunately, nitrates are a byproduct of fish feeding. Fish will be healthier if this parameter is maintained at a low level.

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 water without nitrates to be taken out and replaced with water that has them. I want to be able to control the water quality. 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?

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 must realize that each tank will have its own water change schedule. This is because each tank will have a different bio-load. How much fish is consumed and how many meals are taken is what determines the bio-load. It’s not hard to understand that more fish will be thrown away if there is more food. A decrease in fish and food would mean less waste. This is how we can determine how much waste our produce. Test your water for nitrates to find out how you can measure it.

You will be able to see how your nitrates rise each week if you have a well-stocked 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 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 do a 30% water change. This will result in a 30% reduction of our nitrate levels. Our new nitrate number 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. 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 is only a matter how many water changes it takes.

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