What are the causes of fish incompatibility? It’s not necessarily the temperament of the fish, though this is an important factor. Some fish need softer water, so the PH of the tank water has to be lower. Some fish need warm water whereas some do not. Based on questions submitted by readers, here are examples of some fish that can or cannot be placed in the same aquarium.
Question: Discus and angelfish seem to be very peaceful fish. Can they both be put in a tank together?
Answer: There are many reasons why you can’t mix discus and angelfish. The PH (acid level) of the water is one of the main reasons for keeping them in separate tanks. Most fish can handle a PH of 6.5 to 8 and live very nicely considering 7 is considered neutral. Angelfish do best in the 7 to 8 range on the PH scale. Discus should be in water with a low PH, somewhere between 5 and 6, in order to breed and to have good color. If the PH is maintained at the proper level, the fish will be active, healthy and will be more inclined to breed.
Discus can survive in the higher PH but they will be slower moving and run the risk of acid burns to their gills. Angel fish are one of the quieter of cichlids but they still have an aggression problem. They will nip the fins on slower moving fish, so if angel fish are combined with discus, expect ratty looking discus. If you are going to mix anything with discus, neon tetras are good because they can survive on a lower PH. They are non aggressive as well.
Question: Are kribensis risky in a community tank?
Answer: Putting kribensis in a community aquarium will work very well; as long as you provide rocky areas in the tank so they can feel at home. In nature, kribensis are found around very rocky areas. They are a docile fish but if they breed in your community tank, they will protect their eggs and their young. That is why it is important to have some caves or hiding places for them in order to provide a place where they can lay their eggs and protect their young.
Questions: Are goldfish compatible with catfishes and silver sharks, or will they become prey?
Answer: Goldfish should not be mixed with tropical fish like silver sharks and tropical catfish. The main reason is water temperature. Goldfish are cold water fish and tropical fish require warm water. If you are insistent on mixing the two, put the goldfish in with the tropical fish. Bear in mind, the goldfish will not be as active in a warm water tank. It would work but it’s not recommended.
Sometimes the goldfish will fall prey to some fish but they should do alright in a home community tank. If unsure, keep goldfish in their own tank.
Fish Compatibility in the Aquarium