Are Tetras Aggressive Toward Mollies?

Mollies and tetras are both considered non-aggressive fish and good choices for a freshwater community tank. They are commonly kept together without incident. Choose tetras and mollies based on the temperament of the individual species, and provide elements in your tank environment conducive to peaceful community life. Take some commonsense precautions to help avoid possible conflict.

  1. Fin Nipping

    • Fish with long flowing fins, such as sailfin or lyretail mollies, are more temptation than some tetras can withstand. Schooling fish, like neon tetras, are known for fin-nipping tendencies. Avoid overpopulating your tank and keep species with flowing fins to a minority. Instead choose mollies such as the black molly, pot-bellied molly or female sailfin molly. Always keep these fish in groups of five or more.

    Tank Size

    • An overpopulated tank is probably the largest contributing factor to whether mollies and tetras get along or not. A general rule, to avoid tank overpopulation, is to limit the number of fish in your tank to approximately one inch of fish per gallon of water. This is not an exact science. Get approximate fish sizes by holding a ruler up against the glass of your tank. If you have twenty inches of fish, you should have a 20 gallon tank. Most small-specie tetras will measure between a half to one inch, while mollies typically measure around two inches.

    Species

    • Research the species you intend to include in your community tank. With over 150 species of tetras, there are many to choose from. Select small-specie tetras and keep in schools of five to seven fish. Some of the most popular species include the neon tetra, black skirt tetra, bleeding heart tetra, black neon tetra, cardinal tetra, glowlight tetra and bloodfin tetra. Avoid large-specie tetras such as the pacu and silver dollar tetras.

    Shelter

    • Provide shelter for attack-prone fish to seek refuge. Live and artificial plants add esthetic value as well as a natural place to hide. Commercially available ceramic and plastic shelters are available in many shapes and sizes. Choose shelters with multiple openings for easy escape for any fish that is being pursued. Rocks and any other decorative items also provide a measure of shelter. Mollies bear live young and the shelter you provide will also serve as protection for any young fish born in your tank.