In general, tank water changes should be done once a week. Although small tanks up to about 10 gallons would benefit more from 2-3 water changes instead. Large tanks, on the other hand, are fine with water change every two weeks. This practice is an important part of caring for tropical fish.

Water changes will actually depend on your bioload. This is the amount of waste produced by your aquarium organisms. You will be able to tell if you’re changing your water enough by measuring nitrates once a week, a day or two after a water change. Nitrate levels should decrease or remain the same from week to week. If not, you are not changing water frequently enough.