Aquarium Health Score
A realistic stocking check that goes beyond the "1 inch per gallon" rule — weighing bioload, compatibility, swimming space, water parameters, and schooling together into one score.
Tank Setup
Enter your tank's specs — capacity is calculated from volume, filtration, plant load, and how often you change water.
Build Your Stock List
Add species and quantities. Scores are derived live from each species' size, waste output, activity level, and temperament — nothing here is pre-scored by hand.
Aquarium Health Score
Combines bioload (40%), compatibility (20%), swimming space (15%), water parameters (15%), and schooling (10%) into one overall picture.
Aquarium Health Score
How is this calculated?
Capacity points
"Capacity" isn't litres or gallons — it's a derived index. Your tank's litre volume is multiplied by a filtration factor (weaker turnover lowers it, stronger raises it), then boosted for plant density and water-change frequency, since both help a tank carry more life safely than raw volume alone suggests. It's a comparative number, not a physical measurement.
Used points (bioload)
Each species costs points based on adult size, typical waste output, and activity level for its category, with a gradual (not sudden) size penalty for larger-bodied fish, then multiplied up for more aggressive temperaments, which tend to need more claimed space per fish.
Overall score weighting
- Bioload (40%) — used points vs. capacity
- Compatibility (20%) — temperature/pH overlap and temperament match between every pair of species, plus specific known problem pairings
- Swimming space (15%) — tank length relative to the largest open-water fish's adult length; bottom-dwellers are judged on floor footprint instead, and tall-bodied fish (Angelfish, Discus) on tank height
- Water parameters (15%) — how much temperature/pH range is shared across your entire stock list at once
- Schooling (10%) — whether shoaling species are kept in a large enough group
Hard caps
Some problems shouldn't just be averaged into the overall percentage, because nothing else can compensate for them. A species kept well under its documented minimum tank size, footprint, or height requirement; two species with zero overlapping temperature or pH range; territorial cichlids stocked past their combined territory need; a known predator housed with fish small enough to be food; a documented problem pairing (like fin-nippers with long-finned fish); or multiple individuals of a solitary species — any of these caps the overall score directly, however good the rest of the stock list looks.
A note on the data
Species figures (tank size, adult length, temperature, pH, temperament) are drawn from commonly cited aquarium-keeping references and can vary between sources and between individual fish. Treat every result here as a strong starting guideline, not a guarantee — cross-check anything borderline against our Species & Care Guides or ask at a club meeting before finalising a stock list.
Not Sure About a Stock List?
This tool is a great sanity check, but nothing beats a second opinion from an aquarist who's kept the species. Come along to a meeting and talk it through with members who've been there.
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