How frequently should I do partial water changes?
The more frequent the changes, the less water that needs to be replaced. However, the longer between changes, the more stressful each change potentially becomes, because a larger portion of the water gets replaced. Replacing roughly 25% of your tank’s water bi-weekly is a good minimal starting point, but may not be enough. The proper frequency really depends on such factors as the fish load in your tank. Nonetheless, you should do water changes often enough so that – nitrate levels stay at or below 50ppm, and preferably MUCH lower (less than 10ppm is a good optimal value); – the change in water chemistry resulting from a change is small. In particular, the before and after pH of your tank shouldn’t differ by more than .2 units. (Use a test kit the first few times to get a feel for what’s right.) If your pH changes too much as a result of a water change, perform changes more frequently, but replace less water at each change. Water changes remove nitrates after they’ve been produced. Nit
