The Institute for Aquarium Maintenance Science Institute for Aquarium Maintenance Science Methods · Standards · Stewardship
Instrument · Maintenance Planner

Maintenance Schedule Calculator

Describe your tank, and the Institute will propose a sensible starting cadence for partial water changes — how often, and how much. Treat it as a considered first estimate to adapt, not a verdict.

What this is, and is not

This is a transparent heuristic, not a validated scientific instrument. It turns well-established principles — bioload rises with stocking and feeding; plants and dilution lower nutrients; larger volumes are more forgiving — into one figure. Your own water tests always overrule it. If your nitrate is climbing or ammonia is ever detectable, change water sooner, whatever the number below says. See Water Chemistry.

The actual water volume, which is a little less than the tank's rated size.
More fish, or bigger and messier fish, means more waste.
Uneaten food is a major nutrient source.
See the Filtration guide.
Healthy plants consume nutrients that would otherwise accumulate.

How the estimate is reached

The calculator multiplies a small set of well-established factors into a single "maintenance load" index, relative to a typical mid-size community tank, and maps that index onto a frequency and a change volume:

  • Stocking and feeding raise the load, because they are the sources of the waste and nutrients the water change removes.[7]
  • Filtration adjusts how quickly that waste is processed.[8]
  • Live plants lower the load by consuming nutrients directly.[10]
  • Volume tempers everything: a larger body of water dilutes and buffers change, so it needs proportionally less frequent intervention; a small tank, more.

It deliberately produces round, conservative numbers in the ordinary 20–50% and 3–14 day ranges. It cannot see your actual water — only a test kit can — which is why every output ends with the same instruction: measure, and let the readings decide.