How we check compatibility

Every verdict on this site comes from the same rules applied to the same table of 99 species. No pair is judged by hand.

The species table

For each fish, shrimp and snail we record a temperature and pH range, adult size in a home aquarium, a minimum tank, temperament, where it swims, group size, diet and lifespan. We also note habits that cause trouble: fin nipping, long fins, eating shrimp or snails, latching on to other fish, needing a tank to itself.

The figures are a summary of what published care guides, FishBase and Wikipedia agree on. Where sources differ we take the range most keepers work with, not the extremes a fish survives. The table was checked against these sources in October 2026.

The checks

Water comes first. If the temperature ranges do not overlap, the answer is no. A shared range under 2°F, or a pH squeeze, makes it a yes with care.

Then size. A predator eats fish up to about 45% of its own length. Any large fish that is not a plant eater will swallow fish a fifth of its size. Shrimp are judged by mouth size too, and most fish over an inch and a half eat baby shrimp.

Then behaviour. Fin nippers next to long-finned or slow fish, aggressive fish next to peaceful ones, two territorial species on the same bottom, two labyrinth fish at the surface. Each problem is rated as a deal breaker or a warning, and the worst one decides.

That gives 4,851 verdicts. Each has its own page with the reasons spelled out.

Limits

Fish are individuals. A calm tiger barb exists, and so does a betta that attacks everything. Tank size, plants, and the order fish are added change the odds. Use the verdict as a starting point, watch new arrivals closely, and have a spare tank or a return plan.

Spotted a wrong figure or a verdict that does not match your experience? Write to [email protected].