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Freshwater Fish Compatibility Guide

Which fish can live together? This guide covers temperament, tank size requirements, and a compatibility chart for the most popular freshwater species. Updated October 2026.

One of the most common mistakes beginners make is combining incompatible fish. A betta and a guppy, for example, can lead to torn fins within hours. This guide explains the rules for building a peaceful community tank.

The 3 Golden Rules of Fish Compatibility

1. Match temperament. Peaceful fish go with peaceful fish. A single aggressive species can terrorise an entire tank.

2. Avoid similar-looking males. Many fish (bettas, cichlids, guppies) see lookalike males as rivals. Keep only one male of visually similar species unless the tank is very large.

3. Match water parameters. Temperature, pH, and hardness must overlap. Mixing a soft-water species (discus, cardinal tetras) with hard-water fish (African cichlids) guarantees stress and disease.

💡 Stock Density RuleA common starting point: 1 inch of adult fish per gallon of water — but this is a rough guide, not a law. A single 6-inch oscar needs far more than 6 gallons. Bioload matters more than size alone.

Fish Profiles & Temperament

🐠
Neon Tetra
Peaceful

Min tank: 10 gal | Temp: 72–80°F | pH: 6.0–7.0 | Groups of: 6+ (schooling)

Classic community fish. Keep in groups of 6 or more — solitary tetras become stressed and hide. Pairs well with: corydoras, rasboras, danios, other tetras, guppies. Avoid: bettas (fin-nippers), large cichlids.

🐡
Betta (Siamese Fighting Fish)
Solo MaleSemi-Aggressive

Min tank: 5 gal | Temp: 76–82°F | pH: 6.5–7.5 | Groups: 1 male only

Never house two males together — they will fight to the death. Can live peacefully with: corydoras, snails, shrimp (sometimes), calm community fish with no flowing fins. Avoid: guppies (betta confuses them for rival males), fin-nippers, other bettas.

🦈
Corydoras Catfish
Peaceful

Min tank: 10 gal | Temp: 72–79°F | pH: 6.0–7.5 | Groups of: 4+ (schooling)

Perfect bottom-dwellers for community tanks. They stay out of everyone’s way and clean up leftover food. Pairs with virtually any peaceful species. Use sand substrate — gravel damages their sensitive barbels. Avoid: aggressive cichlids, oscars.

🐟
Guppy
Peaceful

Min tank: 10 gal | Temp: 74–82°F | pH: 7.0–8.0 | Groups: 1M : 3F ratio

Colourful, hardy, and prolific breeders. Keep more females than males to prevent stress. Pairs well with: tetras, corydoras, mollies, platies. Avoid: bettas (bettas attack their flowing fins), large predatory fish, fin-nippers like tiger barbs.

🐠
Platy
Peaceful

Min tank: 10 gal | Temp: 70–80°F | pH: 7.0–8.0 | Groups: 1M : 2F ratio

Excellent beginner fish — very hardy and tolerant of water quality fluctuations. Pairs well with: guppies, mollies, corydoras, danios. Like slightly harder, alkaline water. Avoid: aggressive species, very soft-water fish.

🐠
Angelfish
Semi-Aggressive

Min tank: 30 gal (tall) | Temp: 76–84°F | pH: 6.0–7.5 | Groups: Pair or 5+

Beautiful but will eat small fish. Neon tetras are a common meal for adult angels. Pairs with: larger tetras, corydoras, gouramis, rasboras. Avoid: neon tetras, guppies (too small), other cichlids (territory conflicts), fin-nippers.

🐡
Tiger Barb
Fin-Nipper

Min tank: 20 gal | Temp: 74–79°F | pH: 6.0–7.5 | Groups of: 6+ (reduces nipping)

Tiger barbs kept in groups of 6+ tend to focus aggression on each other rather than tankmates. In smaller numbers they will shred fins. Pairs with: other barbs, danios, loaches. Avoid: bettas, guppies, angelfish, any long-finned fish.

🐠
Oscar
Aggressive

Min tank: 55 gal | Temp: 74–81°F | pH: 6.0–8.0 | Groups: Usually solo or bonded pair

Oscars will eat almost anything that fits in their mouth. Best kept alone or with other large cichlids of similar size. Not suitable for community tanks. Avoid: any fish smaller than 5–6 inches.

Quick Compatibility Chart

✅ = Compatible   ❌ = Incompatible   ⚠️ = Use caution / depends on tank size

Species Neon Tetra Betta Corydoras Guppy Angelfish Tiger Barb Oscar
Neon Tetra — ❌ ✅ ✅ ❌ ❌ ❌
Betta ❌ — ✅ ❌ ⚠️ ❌ ❌
Corydoras ✅ ✅ — ✅ ✅ ✅ ❌
Guppy ✅ ❌ ✅ — ⚠️ ❌ ❌
Angelfish ❌ ⚠️ ✅ ⚠️ — ❌ ❌
Tiger Barb ❌ ❌ ✅ ❌ ❌ — ❌
Oscar ❌ ❌ ❌ ❌ ❌ ❌ —
⚠️ Always Research Individual SpeciesThis chart is a general guide. Individual fish have personalities — some bettas are unusually aggressive, some are calm. Always have a backup plan (a spare tank or divider) when introducing new fish.

Best Beginner Community Combinations

🌈 The Classic 20-Gallon Community

  • 8 Neon Tetras
  • 4 Corydoras Catfish
  • 4 Platies (1 male, 3 female)

✅ Peaceful, colourful, all compatible

🐡 The Betta Showcase (5–10 Gallon)

  • 1 Male Betta
  • 4 Corydoras (pygmy or bronze)
  • 3 Nerite Snails

✅ Low bioload, beautiful centrepiece

🌿 The Planted Tank (30 Gallon)

  • 10 Rummy Nose Tetras
  • 6 Harlequin Rasboras
  • 6 Corydoras
  • 1 Honey Gourami (bonus centrepiece)

✅ Stunning schooling display, all peaceful

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