Choose your tank size, add species, and see a realistic stocking level with group-size and compatibility warnings—based on adult fish sizes, not the ones in the shop tank.
How it estimatesLoad = Σ adult size^1.5 × waste factor
Each fish contributes by its adult size and waste output; capacity scales with water volume and filtration. 80% or less is a comfortable community.
Live planner
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Neon TetraParacheirodon innesi · adult ~3 cm · 21–27°C
10
52% stocked — Comfortably stocked
Based on 100 L of water and adult fish sizes. This is a planning estimate, not a guarantee—research every species before buying.
What it does
Adult sizes, honest numbers.
Shop fish are juveniles: the 3 cm "common pleco" becomes a 40 cm giant, and the inch-per-gallon rule ignores that a fish twice as long produces far more than twice the waste. This planner weighs every species by its adult size and typical waste output, then compares the total against your real water volume and filtration.
It also checks the things stocking numbers miss: schooling species kept in too-small groups, tanks below a species' practical minimum, temperature ranges that do not overlap, and predators mixed with bite-sized tankmates.
Before you buy fish
Three quick checks
01
Cycle the tank fully first—ammonia and nitrite must read zero before any fish go in.
02
Add fish in small batches over weeks so the filter bacteria keep pace with the load.
03
Cross-check adult sizes and behaviour in a species guide; no calculator replaces research.