Freshwater Fish Compatibility Matrix
Most-checked pairings
How we rate compatibility
- Water overlap. Temperature, pH and hardness ranges must share a workable band — not just touch at the edges.
- Size ratio. Anything that fits in another animal's mouth at adult size is treated as prey.
- Temperament. Fin-nippers, territorial cichlids and slow long-finned fish are scored against each other.
- Space. The pair inherits the larger minimum tank, plus room for both groups.
- Diet and speed. Fast surface feeders will starve slow bottom dwellers if feeding is not managed.
Compatibility FAQ
How do you decide whether two fish are compatible?
Five factors, in this order: shared temperature window, shared pH and hardness window, adult size ratio (a fish that fits in another's mouth eventually will), temperament and fin-nipping risk, and the combined minimum tank size once both species have their proper group.
What does “with care” mean?
The pair can work, but one factor is tight — usually a narrow pH or temperature overlap, or a size gap that needs plenty of cover. The individual comparison page states the exact condition to meet.
Are shrimp and snails included?
Yes. Cherry shrimp, amano shrimp, nerite and mystery snails are rated against every fish, because “will this fish eat my shrimp” is the single most common compatibility question we see.
Does a compatible verdict mean any tank size works?
No. Compatibility assumes both species have their minimum group in a tank that meets the larger of the two minimums. Check the figure with the stocking calculator before buying.