Tank Mates and Fish Compatibility Calculator

To ensure a harmonious aquarium environment, use our fish compatibility calculator to determine suitable tank mates. It considers factors like fish size, temperament, and water parameters. This fish compatibility calculator helps prevent issues like aggression, stress, and disease in your fish community.

What to Consider When Choosing Tank Mates for Your Fish?

When selecting tank mates for your fish, keep in mind the fish size, tank size, temperament, and water parameters. These factors will ensure a harmonious and healthy environment for all your aquarium inhabitants.

Fish Size

  • Size matters: Avoid combining large fish with smaller ones; the smaller fish may become lunch!
  • Choose fish of similar size for a more peaceful coexistence.

Tank Size

  • Make sure your tank is big enough for all the fish to comfortably live and grow in.
  • A general rule is 1 gallon of water per inch of fish, but certain species may require more space.


  • A well-balanced tank means combining fish with similar temperaments.
    • Peaceful fish: Tetras, Guppies, and Corydoras.
    • Semi-aggressive fish: Barbs, Angelfish, and some Cichlids.
    • Aggressive fish: Oscars, Piranhas, and certain species of catfish.
  • Don’t mix aggressive fish with peaceful ones to prevent conflicts and stress.

Water Parameters

  • Maintain proper water parameters: pH, temperature, and hardness should be in the appropriate range for each species.
  • Research each fish species’ specific requirements and ensure all tank mates have compatible water needs.

What Happens if You Choose the Wrong Tank Mates?

Choosing the wrong tank mates for your fish can lead to several potential problems, ranging from stress to even death.

In order to provide your tank’s inhabitants with a healthy environment, it’s crucial to understand the consequences of poor tank mate choices.

Stress and Aggression: Incompatible tank mates can lead to increased stress levels and aggression among fish. This not only affects their overall health, but can also cause fighting, fin nipping, and other aggressive behavior.

Effects: Prolonged stress can weaken their immune system, leaving them susceptible to illnesses and infections.

Competition for Food and Territory: Wrong tank mates might result in competition for resources like food and territory, causing some fish to be malnourished or constantly vying for space.

Effects: This could lead to fish becoming undernourished, stressed, and even potentially stunted growth.

Cannibalism: Some larger or more aggressive fish might prey on smaller species if housed together in the same tank.

Effects: Adding smaller or timid fish to a tank with predatory species can lead to the loss of those fish.

Incompatible Water Parameters: Different species of fish have specific water parameters (temperature, pH, hardness) they require to thrive.

Effects: Housing fish together that require different water parameters can weaken the immune systems of one or both fish and lead to various health problems.

Best Aquarium Fish Tank Mates

A well-chosen community of fish tank mates means successfully pairing compatible species and creating a harmonious living environment for all. Below is a list of popular fish tank companions you can consider for your aquarium: