What Kinds Of Fish Can I Keep Together: Fish Compatibility

Gretchen Wiggins
Oct 18, 2022
3 min read

Updated: Nov 5, 2022

Having different types of fish living together in an aquarium can make for a beautiful spectacle. However, if you keep fish together that do not get along, it can end badly. That is why it is important to consider what fish are good to keep together. These are just a few important topics to consider when choosing different fish to put in your tank. I strongly recommend you do further research on the specific types of fish you are considering keeping together. This blog post serves as a guideline for why certain types are or are not compatible.

Saltwater vs. Freshwater

This is one of the most important things to consider because there is no way to get around it. This may be stating the obvious but freshwater fish can not live in saltwater and saltwater fish can not live in freshwater. This means that when choosing fish for your tank you must consider what kind of tank you want to have. For beginners, I suggest starting with a freshwater tank.

Water Parameters

The water parameters of your tank ties into whether you have a freshwater or saltwater tank but also includes other things like water temperature and pH level. Fish come from all over the world so naturally they have adapted differently to the areas in which they inhabit. For this reason you can’t keep different types together. For example, you can’t keep cold-water fish like goldfish together with tropical fish like tetras or danios.

Size

The size of the fish you keep in your tank should also be taken into consideration because if the size difference is drastic, it is likely that the bigger fish will end up eating the smaller fish. A good rule of thumb is that if the smaller fish can fit in the bigger fish’s mouth, it is probably not a great idea to keep them together.

Water Levels

Different types of fish tend to prefer to swim in different areas of the tank. Having a good mix of these types of fish can allow you to have a few more fish in your tank. For example, in my 55 gallon tank. I have angelfish (top dwellers), cherry barbs (middle dwellers), and cory catfish (bottom dwellers). This allows for the different types of fish to occupy their own spaces so as to not get in each other's way.

Level of Aggression

Most people know that bettas cannot be kept with other fish, while this is not always the case, it is because they are known to be very aggressive. If you are deciding to keep an aggressive fish in your tank, again, I strongly encourage you to do your research on the specific type of fish you would like to get. However there are some tips that will help your fish live in harmony.

Make sure you have a large enough tank to where the less aggressive fish can get away without hitting the glass of the tank.
Having a lot of plants and decorations for your fish to hide can make them feel safe.
Keep a very close eye on the tank to ensure your fish aren’t getting too aggressive with each other.
My last tip on keeping aggressive fish together is feed in more than one area of the tank at a time so your fish do not have to fight over the food.

Some Fish Don't Like Having Roommates

While you can try to keep certain types of fish together, some of them just don’t like having roommates. This is partially the reason why bettas don’t do well with tank mates. I will go further into detail on this topic in a later blog post, however, male bettas are threatened by things that resemble another male betta. With that being said, I would like to state a huge disclaimer that even if you keep your betta with a fish that looks nothing like another betta, it is not a guarantee that it will work. Another fish that doesn’t do too well with others is the goldfish. They do well with fish of the same species but typically if you have goldfish, you should only keep them with other goldfish.

If you are looking for specific species that are compatible, check out these links!

Freshwater