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Free aquarium stocking calculator: your online tank stocking tool
27 February 2026
A free aquarium stocking calculator or online aquarium stocking calculator tool helps you plan fish combinations before you buy. You pick a tank size, add species, and see whether your planned stocking fits — bioload, compatibility, pH and temperature ranges. No sign-up, no downloads. Just a tank stocking calculator and fish stocking calculator in one.
Our free aquarium stocking calculator does exactly that. Select your tank (or enter custom dimensions), add fish from our database, and get instant feedback on bioload, compatibility, swim zone balance, and parameter overlap. Same logic as leading fish tank apps like App-aquatic — but you can use it in your browser right now.
What a stocking calculator does
A good aquarium stocking calculator checks three things: bioload (how much waste your fish produce), compatibility (which species get along), and parameter overlap (pH and temperature ranges that suit all your fish). It also flags group sizes — schooling fish need groups of six or more; some species are solitary. See our How to use a stocking calculator guide for full details.
Why use a free online tool?
You do not need to sign up or install an app to plan a tank. A free aquarium stocking calculator in the browser lets you experiment quickly: try different tanks, add and remove species, see the compatibility matrix. When you are ready to commit, you can download App-aquatic to save tanks, track parameters, and get care reminders.
Got fish in mind? Use the tank size calculator
If you already know which species you want, use our tank size calculator instead. Add your fish and we will tell you the tank you need.
Try our free aquarium stocking calculator — no sign-up required.