How much water should you change in your fish tank? Plan it by nitrate

A fish tank can't get rid of nitrate by itself: it just builds up as fish eat and make waste. The fix is fresh water, swapped in a little at a time, usually somewhere between 10 and 30 percent a week.

Use the planner to see where your nitrate would settle, learn why vets and welfare groups say to treat the tap water and match its temperature, and find out when a test result means you should ask an expert.