Fish have to be compatible with each other. Keeping aggression to a minimum in your tank, and preventing your fish from killing and/or eating each other, is likely high on your list of priorities. Choosing the right fish can ensure everything goes well, while making bad stocking decisions can turn your tank into an aquatic battle royale. It is also important to check whether they have the same needs. For example, some fish, such as goldfish, need cold water, while most others are tropical fish, needing warm water.

Let’s understand this a little better. There are literally thousands of species of freshwater fish out there—only some of these are suitable for your aquarium, and others are best kept alone (like in a single fish species tank) or in the company of similar fish (as in cichlids). Out of the fish that can live in your aquarium, some are especially suited for community tanks due to their

Keep These Points in Mind When Checking for Compatibility

  • Research before you buy. This is probably the most important thing you can do as a favor to yourself and all the fish concerned. Check out the chart above for a ready reckoner! 
  • Don’t just go by what the pet store guy has to say about a fish’s compatibility. Look it up yourself. Many fish are shoaling fish, best kept in schools of 10 or more. Some others, such as Siamese fighters, are loners, best kept alone. Similarly, arowanas, flowerhorns, Oscars, and other similar fish will not bother a fish of a similar size, but if that fish can fit into their mouths, they won’t think twice!
  • Provide enough space for each fish. Overcrowding is another cause of aggression and stress amongst tank mates. Remember that each fish is territorial in varying degrees (cichlids are the most aggressive in protecting territory), and you need to ensure you take care of this aspect. Also take special care of their needs. For example, clown loaches, blackghosts, Synodontis, etc. like to stay in driftwood, while cichlids prefer rocky structures with lots of small caves that they can lay claim to.