Water Change Volume

Changing too much water may compromise the beneficial bacteria in your aquarium.

Q. I have a 55-gallon aquarium with an 8-inch red devil. I do water changes twice a week and have two Penguin filters (a 170 and a 125). For water changes, I use tap water (pH 8.0), Biosafe and Seachem Discus Buffer to keep the pH at 7.0. After a water change, it turns slightly cloudy but clears up about the time another change is due. I have thought about changing to a liquid pH reducer to lower precipitating calcium and magnesium. Or maybe I’m cleaning the gravel too much and need to use a bacteria starter with the water changes. What should I do?
Charlie Wainwright
Biloxi, Mississippi

A. Congratulations on doing a good job of the most important aquarium maintenance chore: water changes. You say that you do water changes twice a week, but you don’t say how much of a change you do each time. You may simply be doing water changes that are too large. I suggest no more than 10 percent of the aquarium volume if you stick to the twice-a-week schedule, especially given that you have only one large fish in a 55-gallon aquarium.

It’s possible that with just one large fish, doing large water changes may not be giving the beneficial (nitrifying) bacteria a chance to get established in the water and on the surfaces of the aquarium before you change another large volume of water. It also is possible that there is too much waste from uneaten fish food. Finally, you do not say how much gravel you have and how you vacuum it. If you vacuum the gravel too much, again you may not be giving the good bacteria a chance to get growing. I hope this helps.

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Fish · Freshwater Fish