Free aquarium tools
Three small calculators we kept reaching for. The same math the in-app forecast runs on — only here, you don't have to log anything.
CO₂ calculator
Enter pH and KH, get CO₂ in mg/L. The pH + KH method, without a dropchecker.
Dosing calculator
How many millilitres of your fertiliser get you from current to target? Tank volume in, dose out.
Water-change impact
What does a 30% water change actually do to your nitrate? Or your KH? Mass balance, no spreadsheet.
Hardness converter
dKH ↔ ppm CaCO₃ ↔ meq/L, and dGH split into Ca + Mg. The unit translator for every test kit you'll meet.
Nitrogen cycle timeline
Watch NH₄ → NO₂ → NO₃ over the weeks of a new tank, with sliders for tank size and ammonia source. The chart you wish your fish-in-cycle came with.
Fish-food nitrate calculator
How much NO₃ does feeding actually add? Grams per day, protein %, tank size — out comes the daily nitrate load your filter has to deal with.
Volume calculator
Outer size minus the glass, substrate and the gap below the rim. The real, net litres your tank actually holds — plus US and UK gallons.