How Many Fish Can Be Put in a 50 Gallon Aquarium?

Overcrowding a tank is a quick way to kill fish. How many fish can comfortably live in a 50-gallon aquarium depends on the fish species, the type of aquarium and the size of the tank surface area.

  1. Misconception

    • Many people believe that one inch of fish can fit in one gallon of water, so that 50 one-inch fish could fit in a 50-gallon aquarium. This calculation does not work for brackish water or salt water aquariums, or tall, narrow aquariums.

    Size

    • Many fish grow more than one inch across. Always use the size of the adult fish when making calculations about how many fish can fit in a particular tank. Some aggressive species, like the oscar or velvet cichlid, need 55 gallons for just one adult.

    Considerations

    • Gravel, plants and decorations take up space in an aquarium, leaving less room for the fish and less oxygen content in the water. Only add one or two fish at a time to a tank for a multi-species tank. If the fish start dying, stop adding fish.