Fish Compatibility Checker & Tank Mate Chart

Find out what fish can live together. Pick the species you want and we'll check temperature, pH, temperament, fin-nipping and predation to flag bad tank mates before you buy.

Add the species you want to keep together

Add two or more species to see how they get along.

Compatibility depends on individual temperament, tank size, and aquascape. Use this as a starting guide, introduce new fish slowly, and always have a backup plan.

What makes fish compatible?

Fish make good tank mates when they share four things. Our compatibility checker scores all of them so you don't have to cross-reference a dozen care sheets:

  • Water parameters — overlapping temperature and pH ranges. Soft, warm-water fish and hard, cool-water fish rarely thrive together.
  • Temperament — peaceful, semi-aggressive, or aggressive. Mixing a bully with timid fish ends badly.
  • Adult size — if one fish can fit another in its mouth, it eventually will. Size mismatches mean predation.
  • Fins and behavior — fin-nippers like tiger barbs harass long-finned fish such as bettas, angelfish and guppies.

Which fish are peaceful, and which are aggressive?

As a general guide:

  • Peaceful community fish: tetras, rasboras, corydoras, most plecos, guppies, platies and shrimp-safe nano fish.
  • Semi-aggressive: tiger barbs, serpae tetras, some gouramis and dwarf cichlids — usually fine in the right group size and tank layout.
  • Aggressive / predatory: oscars and many large cichlids — best kept in species-appropriate setups, not peaceful communities.

Shrimp and snails add another layer: many fish that are peaceful toward other fish will still hunt dwarf shrimp.

How to build a balanced community tank

Spread your stock across the tank's levels — bottom dwellers like corydoras and plecos, mid-water schoolers like tetras, and a surface or centerpiece fish. This reduces competition and aggression. Keep schooling species in groups of six or more so they feel secure, and add new fish gradually. Once your community looks compatible here, confirm you have room for them all with our Aquarium Stocking Calculator.

Fish Compatibility — FAQs

What fish can live together?

Fish with overlapping water requirements, similar temperament, and compatible adult sizes generally live together well. Peaceful community fish such as tetras, corydoras, rasboras and plecos are a reliable starting point. Use the checker above to test your specific combination.

What are good tank mates for plecos?

Bristlenose and clown plecos are peaceful bottom dwellers that suit almost any community — tetras, rasboras, corydoras, livebearers and peaceful cichlids all work, as long as the tank is big enough for the pleco's adult size. Avoid housing multiple male plecos in a small tank, as they can be territorial.

Why are my fish fighting?

Common causes are mixing aggressive and peaceful species, keeping schooling fish in too-small groups, overcrowding, or not enough hiding spots and territory. Check your combination above and make sure each species has the space and numbers it needs.

Can I keep aggressive and peaceful fish together?

Usually not. Aggressive species stress, injure, or eat calmer tank mates. If you want an aggressive species like a large cichlid, plan a tank around fish with similar temperament and size rather than a peaceful community.

Will my fish eat my shrimp?

Many will. Most fish larger than about two inches see dwarf shrimp as food. Nano fish like chili rasboras and ember tetras, plus snails and other shrimp, are the safest companions for a shrimp colony. The checker flags shrimp-safe combinations for you.