TankMatcher · Compatibility reference · Published November 5, 2026
Freshwater fish compatibility reference
Four example pairings calculated from the same curated species data and compatibility rules as the interactive checker. These are planning screens, not promises of successful cohabitation.
Four checker-derived pairings
Minimum gallons are the pairwise species minimum before stocking density and schooling/group footprint are considered. Shared water ranges are intersections of each species' maintained attributes, not ideal setpoints for every fish.
Data and verdicts from the current TankMatcher compatibility checker| Pairing | Verdict | Minimum tank | Temperature overlap | pH overlap | GH overlap |
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| Betta + Neon Tetra | Conditional | 10 gal | 76–78°F | 6.5–7.5 | 3–10 dGH |
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| Neon Tetra + Cardinal Tetra | Conditional | 15 gal | 75–78°F | 6.0–7.2 | 1–8 dGH |
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| Oscar + Neon Tetra | Do not mix | 75 gal | 74–78°F | 6.0–7.5 | 5–10 dGH |
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| Betta + Cardinal Tetra | Conditional | 15 gal | 76–82°F | 6.5–7.2 | 3–8 dGH |
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Behavior and group-size considerations
Notes below are taken from the checker's reason messages and the maintained species-care caveats. A general fin-nipping caution is not the same thing as a pair-specific fin-nipping issue flagged by the engine.
Betta + Neon Tetra — Conditional
- Neon Tetra should be kept in a group of at least 6, not as a single add-on.
- Keep one male per tank; two males fight, and males with females typically need a sorority-style setup with planning and backup tanks.
- Avoid fin-nippers (tiger barb, serpae tetra, black skirt tetra, large danios) — long fins make bettas easy targets.
Neon Tetra + Cardinal Tetra — Conditional
- Neon Tetra should be kept in a group of at least 6, not as a single add-on.
- Cardinal Tetra should be kept in a group of at least 6, not as a single add-on.
Oscar + Neon Tetra — Do not mix
- Neon Tetra is prey-sized compared with adult Oscar.
- At least one species is highly territorial or aggressive; only attempt this in a carefully planned tank.
- Neon Tetra should be kept in a group of at least 6, not as a single add-on.
- Adult oscars can eat small tetras.
- Predatory: small tetras, rasboras, dwarf shrimp, and snails are food, not tankmates.
Betta + Cardinal Tetra — Conditional
- Cardinal Tetra should be kept in a group of at least 6, not as a single add-on.
- Keep one male per tank; two males fight, and males with females typically need a sorority-style setup with planning and backup tanks.
- Avoid fin-nippers (tiger barb, serpae tetra, black skirt tetra, large danios) — long fins make bettas easy targets.
How to read the verdicts
- Compatible (green)
- The current checker flags no major conflict in its covered attributes. This is a preliminary indication, not an unconditional safety rating.
- Conditional (yellow)
- Potentially workable only after the identified group, behavior, tank layout and water-parameter concerns are addressed.
- Do not mix (red)
- A major risk such as predator/prey conflict makes the pair unsuitable for routine community stocking, even when the water ranges overlap.
Planning screen — not a guarantee
Results use curated husbandry attributes and conservative pair rules. Individual temperament, mature adult size, filtration, tank footprint, actual water chemistry, stress and long-term observation matter. A minimum tank value is not a complete stocking recommendation. Verify care with current husbandry sources and have a separation plan before adding fish. Evidence coverage varies by species; the checker does not claim a uniform confidence level for every pair.
Open compatibility checker Read methodology and confidence definitions