manfred · the workbench
Free aquarium tools
A few small calculators we kept reaching for. The same math the in-app forecast runs on — only here, you don't have to log anything.
- 01
CO₂ calculator
Enter pH and KH, get CO₂ in mg/L. The pH + KH method, without a dropchecker.
- 02
Dosing calculator
How many millilitres of your fertiliser get you from current to target? Tank volume in, dose out.
- 03
Water-change impact
What does a 30% water change actually do to your nitrate? Or your KH? Mass balance, no spreadsheet.
- 04
Hardness converter
dKH ↔ ppm CaCO₃ ↔ meq/L, and dGH split into Ca + Mg. The unit translator for every test kit you'll meet.
- 05
Nitrogen cycle timeline
Watch NH₄ → NO₂ → NO₃ over the weeks of a new tank, from tank size and daily ammonia dose. The chart you wish your fish-in-cycle came with.
- 06
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.
- 07
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.