Compatible Fish Groups

To keep your fish healthy and happy, only include compatible species in the same aquarium. Compatible species share similar requirements for food, temperature and water quality. As long as they aren't overcrowded, many species can thrive in a community tank. You may need to add fish one at a time, however, to make sure you aren't overcrowding their habitat.

  1. Small Aquariums

    • Aquariums of 15 gallons or less can house several fish. Tetras, guppies, dwarf gouramis and albino catfish can co-exist peacefully in such aquariums. These tropical fish like a warm aquarium and tend to swim in small schools together. Choose four or more of the same species to provide your fish with enough companions to make them feel comfortable in the aquarium. When choosing guppies, select one male for every two females to prevent males from shredding each other's colorful fins.

    Live Bearers

    • Many species of live bearers can inhabit the same aquarium. Swordtails, mollies, platies and danios can be housed together, for instance. Larger fancy-tailed guppies can also be kept with this group. These fish do best in small groups of their own kind, so always purchase two or more of the same species for the community. All need warm, fresh water, adequate filtration and similar tropical fish food. Because they are live bearers, you may want to invest in a breeding box, or a small plastic or net box that can be suspended in the larger aquarium. Pregnant female fish can be moved into the breeding box to give birth. This prevents other fish from consuming the newborns.

    Semi-Aggressive Species

    • Another compatible group consists of semi-aggressive species. These fish may prey upon smaller, placid live bearers. Large tetras, such as the Buenos Aires tetra, fall into this category, along with silver dollars and blood parrots. Giant danios, large or giant gouramis and severums can also be kept in groups together. It's a good idea to provide groups of plants or rocks in an aquarium with aggressive species. This provides places for fish to hide in the event they are being chased by a more aggressive community member.

    Aggressive Species

    • Many larger tropical fish are too aggressive to house with any but a few of their own kind of selected compatible species. Oscars can be housed in the same aquarium with pacus, plecostomus catfish and white-tip sharks. Cichlids are one of the most aggressive fish species and can only be housed with other cichlids. Oscar fish can grow up to 14 inches. A good rule of thumb with large species is one fish per 25 gallons of water, as long as there is a good filtration system in place.