Fish Compatibility Checker
Pick fish, shrimp, and snails to compare — get an instant color-coded matrix with a plain-language reason behind every verdict.
- Neon tetra
- Guppy
- Betta
- Corydoras catfish
- Angelfish
- Cherry shrimp
| Neon tetra | Guppy | Betta | Corydoras catfish | Angelfish | Cherry shrimp | |
|---|---|---|---|---|---|---|
| Neon tetra | ||||||
| Guppy | ||||||
| Betta | ||||||
| Corydoras catfish | ||||||
| Angelfish | ||||||
| Cherry shrimp |
- Compatible
- Caution
- Not compatible
Select any cell to see the reasons behind the verdict.
Pairs to watch
- Neon tetra + GuppyCautionTheir water-hardness ranges barely overlap.
- Neon tetra + BettaNot compatibleAn aggressive species will harass a peaceful one.
- Neon tetra + AngelfishCautionThe larger fish may eat very small tankmates.
- Guppy + BettaCautionA betta may flare at bright, flowing fins.
- Betta + BettaNot compatibleTwo male bettas will fight — keep only one.
- Betta + Corydoras catfishNot compatibleAn aggressive species will harass a peaceful one.
- Betta + AngelfishCautionTwo boisterous species — watch for tension.
- Betta + Cherry shrimpCautionThis fish may hunt dwarf shrimp.
- Angelfish + Cherry shrimpNot compatibleThis fish may hunt dwarf shrimp.
How we calculate
For every pair we first compare water-parameter ranges: temperature, pH, and hardness (gH). If two species share no range at all, the pair is marked incompatible; if the shared window is very narrow, we flag a caution — one of them would live at the edge of its comfort zone.
We then look at behavior: temperament (an aggressive species next to a peaceful one), adult size (a fish more than three times longer than its neighbor may treat it as food), and known fin-nippers kept with long-finned or placid tankmates.
Generic rules can't capture everything aquarists know, so well-documented special cases override them — two male bettas are always incompatible, angelfish are flagged with dwarf shrimp, and so on. The final verdict for a pair is the worst of all triggered checks.
Frequently asked questions
- Can the checker guarantee two fish will get along?
- No. Individual character, tank size, planting, and stocking order all matter. The matrix shows documented risks so you can avoid known-bad combinations — treat “compatible” as “no known conflicts”, not as a guarantee.
- What do the three symbols mean?
- A check mark means no known conflicts. An exclamation mark means the combination can work but needs care — read the reason before deciding. A cross means the pair is best avoided.
- Why does a pair get a caution when both species like the same water?
- Compatibility is more than water chemistry. Cautions also come from behavior — size differences, boisterous temperament, or fin-nipping — even when temperature, pH, and hardness align perfectly.
- How do I share or print my matrix?
- Share copies a link that restores your exact species set for anyone who opens it. Print opens your browser's print dialog with a clean, printer-friendly chart — handy to take to the fish store.
How to choose tank mates that actually get along
Start with water: temperature, pH, and hardness ranges must genuinely overlap — not just touch at the edges. A fish that merely survives at 24 °C while its neighbor thrives there will be stressed for life, and chronic stress is the number-one cause of disease in community tanks. That's why our checker treats a very narrow shared window as a warning rather than a pass.
Behavior sinks more communities than chemistry does. A single boisterous fin-nipper can shred a betta's fins in a weekend; a peaceful but large fish will eventually eat anything that fits in its mouth. Compare adult sizes — the cute one-inch juvenile in the store may quadruple — and check temperament before you fall in love with a species.
Invertebrates deserve special care. Dwarf shrimp are a snack for most cichlids and even for some otherwise-peaceful fish, and snails are helpless against loaches. If you want a shrimp colony, build the fish list around it, not the other way round.
A compatibility chart tells you which species can share a tank — it doesn't tell you how many. Once your set is conflict-free, run it through our stocking calculator to check whether your tank volume, schooling minimums, and filtration can actually carry it.