Fish Compatibility Checker
Pick any two species from the database and get a realistic compatibility assessment: temperature and pH overlap, temperament, adult size, and the minimum tank the pair needs —plus the risks and exceptions that generic charts leave out.
How It Works
Compatibility is never a simple yes/no. The checker evaluates five aspects in order: temperature overlap, pH and water chemistry, temperament (peaceful, semi-aggressive, aggressive), adult size ratios and predation risk, and finally the minimum tank size that satisfies both species. Well-known combinations carry an editorial verdict with real-world context —the rest are scored from species data, and every result explains why, so you can make the final call for your own tank.
FAQ
Can bettas live with other fish?
Sometimes. A single male betta can work with small, fast, non-flashy tank mates in a 15+ gallon planted tank —but it depends on the individual. Never keep male bettas together, and avoid fin-nipping species or other surface-dwelling anabantoids.
Can angelfish live with neon tetras?
We do not recommend it. Adult angelfish routinely eat adult neon tetras —in the wild, neons are a natural prey item. Larger tetras like black skirt tetras, or deeper-bodied rasboras, are safer mid-level companions.
What makes fish incompatible besides aggression?
Water chemistry (no overlap in temperature or pH ranges), adult size ratios (a fish that fits in another's mouth eventually will be in it), and activity mismatch —hyperactive danios stress slow, long-finned fish even without direct aggression.
Why does the checker say Conditional instead of Compatible?
Conditional means the pairing can work with specific precautions —enough tank size, plants and sight breaks, the right group sizes, or accepting that some individuals won't tolerate the arrangement. Read the risks and exceptions before committing.
How should I introduce new tank mates?
Rearrange decorations before adding newcomers (to reset territories), add fish after lights-out, feed well beforehand, and watch closely for the first few days. Have a separation plan ready —a breeder box or a second tank.
Related Tools
Source: Aquarium Forge editorial guidelines · Last reviewed: