How we check
Five checks, in this order. Every value shows its source. No single score.
1. Room to grow
Fish are drawn at typical adult length. Swimming length starts at three adult lengths for sedentary fish, four for moderate swimmers and six for active swimmers. Curated minimums can increase that requirement. Bottom dwellers and territorial species also need floor space; more height or a bigger filter does not create it.
2. Water you can actually use
We start with external dimensions and subtract glass from both sides of length and width and once from height. Water height also allows 2.5 cm freeboard and the substrate depth; rocks and wood displace a further estimated amount. Presets use nominal manufacturer sizes; measure your own tank for a better estimate.
3. Shared water conditions
We intersect the temperature, pH and hardness ranges of every animal and plant. An empty overlap blocks the plan; a narrow overlap warns that there is little room for error. Some known pairs also have explicit long-term care conflicts.
4. Peaceful neighbours
Known pair rules take priority, followed by checks for fin-nipping, predation, aggression, crowded swim zones and territorial floor area. No compatibility rule can guarantee an individual animal’s behaviour. Observe the community and provide cover.
5. A proper group
Schooling fish receive a warning below their curated group minimum. Social livebearers receive a note below three. A Fix button adds the missing companions, then checks the whole plan again.
6. Bioload and maintenance
Adult length estimates body mass; diet adjusts estimated waste. We compare relative load units with true water volume and filter turnover to report low, moderate, heavy or unsustainable load. Plants offer a modest adjustment. These are provisional heuristics, not measured nitrogen or a nitrate prediction. Use water tests to adjust maintenance.
Evidence, not certainty
Every care value carries a source and confidence level. The first dataset was authored from general husbandry knowledge and is marked “curated-v0 (needs expert review)”. Low-confidence estimates are identified. The current rules need expert calibration; a “Works” result is a planning aid, not a guarantee. Cycle the tank before adding animals.
Your plan stays with you
There is no account or database. Your plan is stored in the link. Display preferences stay in this browser. Share that link to restore the exact tank, equipment, animals and plants elsewhere.