Planner · Aquarium
Check the stocking, compatibility and water parameters before you buy fish
Pick a tank size, filtration rate and target temperature, then add the species you are considering. See at a glance whether the bioload fits, whether the water suits everyone, and which species need a rethink — before anything goes in.
Tank & water
inputsFish & inverts
0 speciesNo fish yet — add a schooling tetra or a cory crew to see the stocking bar move.
Tank view
elevation + zonesSpecies detail
adult figures| Species | Qty | cm | Min L | Temp °C | pH | Zone | Temper |
|---|
What to fix before you buy
How the numbers are worked out
Every figure below is arithmetic you can check by hand. Nothing is fetched from a server.
Volume & turnover
Volume = length × width × height ÷ 1000 in litres; US gallons = litres × 0.264172. If you fill the Litres field it overrides the dimensions. Turnover = filtration L/h ÷ litres, in ×/h. The 4–8×/h target is a freshwater community convention.
Bioload & stocking
Bioload units = Σ qty × adult_length^1.5 × bioload_factor. Score = (bioload ÷ (litres ÷ 10)) × 4, clamped 0–120. Bands: 0–25 understocked, 25–60 comfortable, 60–90 full, 90–120+ overstocked. Bioload factor 0.2–1.5 reflects waste per centimetre (shrimp low, plecos high).
Parameter overlap
Temperature overlap = [max of every low, min of every high]. Same for pH. If low ≤ high there is a common band; its midpoint is the suggested setpoint. If low > high there is no band that suits every species. Figures are typical care-sheet midpoints, not a single vendor's sheet.
Compatibility
Minimum-tank is per-species; schooling is flagged when qty < schooling_minimum. Temperament flags include aggressive with peaceful, tiger-barb fin-nipping long-finned tankmates, and bottom-zone crowding when >6 bottom individuals or >3 bottom species compete for food. Preset values are rounded, textbook-typical care data.
What this is not: a rule-based guide built on widely published care data, not a substitute for species-specific research; every tank and every individual fish differs.
Questions
How is stocking level calculated?
Each fish contributes bioload units equal to quantity × adult length^1.5 × bioload factor. Those units are divided by tank litres ÷ 10 and mapped to a score. Under about 25 is understocked, 25–60 comfortable, 60–90 full and above 90 overstocked. The method section documents the exact bands.
What counts as compatible for temperature and pH?
The tool intersects every selected species' published temperature and pH ranges. The overlap is the only band where all species are inside their tolerance. If the bands do not overlap, no single setpoint suits everyone and the planner tells you which species disagree.
How much filtration does a freshwater tank need?
Aim for 4–8× turnover per hour — filtration litres per hour divided by tank litres. Lightly stocked, planted tanks can sit near 4×; heavily stocked communities or messy eaters should be near 6–8×. The planner flags turnover below 4× and when the bioload calls for more flow.
Can cold-water and tropical fish live together?
Rarely. Cold-water species such as White Cloud Mountain Minnows prefer 14–22 °C while tropical tetras and gouramis need 24–28 °C. Their temperature bands do not overlap, so the planner reports no common setpoint and recommends you choose one thermal group.
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