Need to speak with a Vet Doctor?

Freshwater Aquarium Fish Compatibility

In designing your ideal freshwater aquarium, start with the species you would like to have. If you’ve ever dreamed of your ideal aquarium, take some time and list the species that you would most like to have. Now is the time to consider a few key points when mixing species together in an aquarium.

before you start

Before purchasing your desired fish, take some time to plan out some important tank functions.

Volume and layout

Each species of fish has specific considerations about how much space a fish needs. And it can be a certain type of space, like sandy, rocky, lots of plants, or isolated caves. Community-oriented Pisces may like to live in large groups while others want plenty of space to themselves. Depending on the species you want to mix, take some time to determine how much space they would all take up. Can you fit the volume and any decor you want?

Water quality parameters

With freshwater fish, especially cichlids, some water quality parameters cannot be mixed. If one type likes hard water with high pH and the other can only tolerate low pH and soft water, don’t try to balance them in the middle. If the pH, temperature or kH (alkalinity) do not match, neither will the fish.

Aggressive behavior

Aggressive nature is species-specific. Sometimes captive-bred individuals are more used to living in close quarters, but this is not guaranteed. The more aggressive freshwater fish (link to other article) should be mixed very carefully. Always add the most aggressive fish last, so that other, less aggressive, but still ornery fish can settle in their places.


If you plan to breed your fish, make sure there is more volume in your tank to hold your offspring! Breeding fish is a fun project for any fish owner, but keep in mind that some fish become very aggressive in breeding areas. Different species like different types of areas to grow their young. Be it soft sand, a large cave, or an area with little water flow. Make sure there is enough space in your tank for parents to get their jobs done and not bother their neighbors.

READ ALSO  Molynesia - species, reproduction and care

Ideal freshwater community tank

In an ideal tank, all fish, regardless of their aggressive nature, would have room to live and thrive. Once you have adjusted your fish to the water quality parameters, maintaining good water quality goes a long way towards keeping your aquarium healthy.

What is the best environment for your fish?

Should it be rocky, sandy, planted, or a combination? Depending on where your fish live, how they feed, and what breeding methods they use, you may need to become an aquascaper to create the ideal marine life for your particular fish combination. If you choose different species of fish, could they all live in the same environment? Choose more community-oriented fish that can get by in a smaller space and enjoy the same environment. You may not need to divide a very large tank into different zones for different types.

Do your fish eat the same diet?

Aggressive fish can cause the greatest pain during meals. When you have a wide mix of types and behaviors, feeding them can be a complicated process. When you have a combination of species spread across the herbivore, omnivore, and carnivore spectrum, making sure each fish is getting its intended diet can be a difficult and complicated process. If you choose fish that has a similar diet, you can enjoy it more and worry less about who is having who for dinner.

Where your fish feed in the water column is a consideration few pet fish owners give before starting their tank. Many freshwater fish feed on the surface or in the entire water column. But staple foods like algae eaters and loaches often search the substrate for their meals. Can you guarantee that enough food will get to the bottom of your tank? Spreading meals out in your tank can cut the competition significantly, as long as everyone has enough to eat.

READ ALSO  Mourners - small fish for beginners | Pets

Best freshwater community aquarium fish

Neon Tetra (Paracheirodon innesi)

The Neon Tetra is bright and straightforward and a great addition to any community freshwater tank. Although neon tetras are easy prey for more aggressive fish, they like to go to school together, don’t take up much space, and aren’t fussy eaters.

Neon Tetra. Mirko_Rosenau / Getty Images

Panda cory cat (Corydoras panda)

These little scavengers have a unique black and white color pattern that gives them the “panda” descriptor. Accustomed to living in small groups of 6 or more, these fish sift through fine substrate and collect lost food scraps. They get along with many different species of fish, making them ideal members of the community.

dangercorpse / Flickr / CC by 2.0

Platys, mollies and guppies

The number of breeds and varieties of these live fish is immense. All of these strains are loose, nonprofit fish. Note, however, that live carriers reproduce very quickly. If you can’t separate males and females, you will likely start out with a lot more fish than you expect. Many pregnant moms have been adopted and given birth to several within a few days of adding them to your aquarium.

Brian Kilford / Flickr / CC by 2.0

Fish to Avoid in Community Tanks (Link to aggressive article)

Schleier Angel Fish (Pterophyllum scalare)

Many a freshwater aquarist started with a small group of loose veil angelfish and ended up with several angelfish tanks. Although they can get along as teenagers as they get older, most groups of angelfish will have a dominant abuser. Once that fish has been removed, another will take its place until you have multiple tanks of one fish.

READ ALSO  Gurami - learn the secrets of these fish | Pets

Christophe Archambault / Getty Images

Bucktooth Tetra (Exodon paradoxus)

Don’t be fooled by the “Tetra” name! These are not like their other Tetra cousins. The Bucktooth Tetra are disgusting tongs that love to try to bite something shiny, probably another fish! They also don’t play well with their own species, give them plenty of space and only one fish per tank.

bertrand.sant / Flickr / CC by 2.0

Convict Cichlid (Archocentrus nigrofasciatus)

The convict cichlid is just one of many aggressive cichlid species. If you want to get involved with cichlids, there are many other species and personalities that you need to get to know before you get started. Many cichlids need a certain density in order to thrive. If you are a little underpopulated or overpopulated, your fish will become more aggressive.

Wiljoj / Getty Images

Freshwater Community Aquarium Tips

It’s always best to plan ahead! If you haven’t bought supplies or equipment, start with a list of the types you want and go from there. If you’ve already bought the tank, plan your type carefully.

If possible, always drive with a larger tank. This gives you space in case some of your fish don’t read the rulebook.

Always add the most aggressive fish at the end and give the shy fish plenty of places to hide. Pay special attention to the behavior of your fish during feeding time so that everyone gets a fair share without being bothered.