Fishless cycle simulator

Cycle a tank in five minutes instead of five weeks

Put your real numbers in and watch what your filter is actually doing. Most people take four to six weeks. Some never finish at all — and this shows you why.

Tank volume

litres of water

Your ammonia

% — clear, no surfactants

Temperature 25.0 °C

axolotl fast cycling

pH 7.6

KH — carbonate hardness 8 °dKH

GH — general hardness 10 °dGH

Nitrate in your tap water 0 ppm

Head start

Don't know your KH, GH or pH?

Then that's the first thing to fix, because you're about to spend a month guessing. Tap water in the UK swings from almost distilled in parts of Wales and Scotland to properly hard across the south east — and the difference decides whether your cycle finishes or stalls.

Your water company publishes hardness for your postcode, which gets you close. A test kit gets you right, and you'll need one during the cycle anyway.

Nothing here replaces testing your own water. It's a model — a good one, but the tank on your floor is the real thing.

Ammonia

0 ppm NH₃

Nitrite

0 ppm NO₂

Nitrate

0 ppm NO₃

Readings shown as an API card would show them. The true value is underneath, and the gap between the two is why a cycle feels stuck for a fortnight.

Ammonia Nitrite Nitrate

Cycled

0 days