Tropical fish, especially the freshwater variety, are a popular choice for aquariums because of their bright colors. But when it comes to having different fish in the same tank, their compatibility needs to be taken into consideration. Choosing species of fish to be kept together is an important decision. You need to take into account the aesthetics that you have in mind and also the fact that you don’t want fish fighting or killing each other. Hence, it is important to consider various factors before deciding the types of fish for your aquarium.

Type of water

This one’s a no-brainer. Freshwater and seawater fish cannot live together.


Tropical fish can be broadly classified into three types according to their nature.

  1. Peaceful (eg. Guppies, tetras, and danios)
  2. Semi-aggressive (eg. Barbs, loaches, and eels)
  3. Aggressive (eg. cichlids, plecos, and Oscars)

Peaceful tropical fish of different types can easily live together. You just need to ensure that there is plenty of space in the tank for them. This is to avoid toxic built-up and make cleaning easy.

Peaceful tropical fish can be put together with semi-aggressive fish. But the fish tank needs to be big enough for the fish to comfortably co-exist. Also, there should be enough hiding places within the tank for the fish to have some alone time. This keeps the weaker fish’s stress in check. The size difference between the two types should also be less.

Semi-aggressive fish can also be put together with aggressive fish. But in this case, too, places to hide within the tank are required and do be mindful of the size difference.

Aggressive fish living with aggressive fish is again a difficult situation and requires caution and care. Many aggressive fish of the same type living together might attack, injure, or even eat one another. Hence, keep an eye out if you have aggressive fish.

Sometimes, two fish of the same type also do not get along with each other. Be prepared to move fish into a separate tank if they display aggressive behavior.

Large fish usually bully the smaller ones. In such cases, medium size fish or schooling fish stand a better chance.

Eating patterns

It is advisable to keep fish with similar eating patterns together. Some fish feed slowly, while others quickly gobble up whatever is available.

Some fish eat algae and switch to other food if algae are not available. Fish like the plecos are friendly as long as they feed on algae, but might turn aggressive when feeding on other food.

The above feeding factors need to be kept in mind before deciding which fish you want in the tank.

Water temperature

All types of tropical fish generally require aquarium water to be kept at 79 to 81 degrees Fahrenheit. However, it would make sense to go through the fish profiles you are considering, in order to know whether they would be able to stay together at a single optimum temperature.


Some fish do not get along with fish of the same sex, while some do. For example, the male Betta needs to be the only male in the tank, whereas the female Bettas get along well.