Method and sources
What the planner calculates, with the actual numbers, and where it stops being reliable.
Independence
This site is not the former acrylic aquarium shop in Blissfield, Michigan that once used the name. It sells nothing, takes no commission from any fish, tank or equipment, and carries no advertising. It is guidance, not authority: a local fish keeper, a vet or the people you buy from know your water and your fish better than a table can.
The four checks
Each verdict is level 0 (Fits), 1 (Tight) or 2 (Over). They are never averaged.
| Check | What is compared | Rule |
|---|---|---|
| Space | Longest tank side against each species swim length | Swim length is four times adult length, or the stated minimum tank length if larger. The minimum tank volume also counts, with extra litres for each additional fish. |
| Load | Summed bioload against usable water | Usable water is 85 per cent of brim volume. Bioload weights are raised to the power 0.6, and 2.5 litres is allowed per unit of weight. Within 15 per cent of the limit reads Tight. Marine stock uses a factor of 1. |
| Water | Overlap of temperature, pH, hardness, salinity | Minimum shared overlap: 2 degrees C, 0.3 pH, 2 dGH, 0.002 specific gravity. Less than that reads Tight; none reads Over. Fresh, brackish and marine fish never share. |
| Group | Group size, sex ratio, temperament, predation | Minimum shoal sizes, territorial and fin-nipping flags, and prey size against mouth size. A short table of known pair exceptions overrides the general rules. |
The same sums run in your browser as you add fish. The stocking guide explains them in plain language.
Equipment sizing
The equipment sheet takes the shared temperature range of the stock, picks the midpoint, and sizes a heater from the gap to room temperature and the usable volume. Filter flow is usable volume times a turnover figure set by the heaviest feeder, adjusted for the flow style the species prefer and increased for marine systems. Light is the dimmest class in the stock, in lumens per litre. These are planning ranges, not product recommendations.
Estimated figures
Where a species has no reliable figure, the page marks the value as estimated and the planner treats it with less confidence. Common examples are bioload weight for rarely kept species and minimum shoal sizes. If you know better, treat your own experience as the source.
The data
The table covers 1,000 freshwater, brackish and marine aquarium species. Descriptions and silhouettes were written and drawn for this site, and the silhouettes are stylised, not portraits. Invasive species carry a neutral note rather than advice either way. Health and disease treatment are outside the scope of the site; a vet or a specialist shop should help there.
Known limits
- It assumes a mature, cycled tank with decent filtration. See cycling.
- It does not model plants, sumps, or heavy feeding and water changes.
- Wild-caught and tank-bred fish of one species can differ in hardness and temperament.
- Marine tanks are far less forgiving than the numbers suggest. Read the marine note.
Start with the planner or browse all fish.