We are often asked “how big a water change should I give my aquarium?”. A good water change is the best thing that can be done for just about any aquarium, so I would say “change as much as you can.”

The basis of a water change is to take “bad stuff” out and put “good stuff” in. The more you can take out, and the more you can put in, the better – up to a point.

Maintaining an aquarium’s stability is very important, and changing over 50% of the water in a saltwater tank can be too much change and can create  various forms of shock to fish and corals.

At a minimum, I would say to change out at least ten percent. There are varying opinions on this, but generally speaking, ten percent each week is a fairly good amount to change, especially if you’re skilled at efficiently taking the “bad stuff” out.