How Many Fish Can a 30 Gallon Tank Hold?

Tank overcrowding is one of the most common fish-keeping mistakes. Too many fish in too little space will cause poor water quality and unhealthy fish. Calculating how many fish you can keep in a 30-gallon freshwater tank involves a variety of factors.

  1. The Basics

    • A commonly used baseline is to allow 1 gallon of water per inch of fish. But you also need to consider the sizes and temperaments of the fish, and how the tank will be set up.

    Remember

    • Figure out how many fish you can keep based on how big the species will be when fully grown, not just how big they are in the fish store.

    Fish Factors

    • The size of fish you choose makes a difference. Ten small fish do not have the same need or impact as one 10-inch fish. Larger fish also produce more waste. You will also need to check into the likes and dislikes of particular species. Some fish are more territorial than others.

    Tank Factors

    • Some fish like a heavily planted tank, or one with terrain formed by rocks or driftwood. But keep in mind that decorations, gravel and plants reduce the tank's water capacity. But there is an upside to having plants; they will absorb and break down waste.

    Tip

    • Only bring home a few fish at a time. Once those have settled into the tank well (allow about a week), you can add more.