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Fish Compatibility


The following are "guidelines" for choosing your group of fish. However, remember all fish have individual personalities, and there may be exceptions to the rules. Please read about each individual fish in our fish section before purchasing to make educated decisions. We cannot guarantee fish behavior.

Predatory Fish-Only Tanks - The following fish can be housed together in a predatory tank, but please also read our general guidelines below.

  • puffers
  • groupers
  • triggers
  • lionfish
  • predatory wrasses
  • large angels
  • large tangs
  • large butterflies
  • squirrelfish

There are two types of predators:

  • Nippers - These predators (such as triggers) nip at their prey bite by bite until dead. Prey size does not matter.
  • All-in-one gulpers - These predators (such as groupers, lions, and anglers) will only eat prey they can take in one gulp. If the prey is not small enough to swallow whole, they're not interested.

    Peaceful Reef Tank - The following fish can be housed together in a peaceful reef tank, but please read our general guidelines below.

    • green chromis
    • pygmy angels
    • bassletts
    • pseudochromis
    • small tangs of different shapes
    • anthias
    • small reef-safe wrasses
    • gobies
    • blennies
    • clownfish
    • damsels - but beware as they often become aggressive

    General Guidelines for Adding Fishes:

    • Quarantine.
    • Be careful when housing fish of the same size, shape, and/or colors together, especially if they are from the same genus.
    • Some fish are okay to pair or school if we explicitly state it under our individual fish descriptions. Read fish descriptions carefully as some fish such as clowns must be added at the same time.
    • Mix angels from different regions. For example, an angel from the Red Sea can usually be kept with an angel from the Indo-Pacific.
    • Add more aggressive fish last. Allow peaceful fish to set territories first.
    • Any time you are concerned two fish may fight, add them at the same time so they can establish separate territories. If you add one first and then the other, the whole tank becomes the first fish's territory - not good.
    • When adding more than one fish, add one pair or add in odd numbers. (2, 3, 5, etc. - Not 4, 6, 8, etc.)

    How can I stop my fish from fighting?

    • Sometimes rearranging some of the rock in your aquarium will prevent squabbles by creating new territories and breaking up old “established” territories.
    • Create new hiding places using the rocks.
    • Make sure your fish are well fed. Fat predators are not as likely to harass their tank-mates.

    What should I do if certain fish will not stop fighting?

    • At this point you must remove the aggressive fish from your aquarium.
    • If you have trouble catching them try dropping some of their favorite food on the surface and catch them quickly with a net when they come up to eat it.
    • If you still can’t catch them try using a trap.

    How do I know a fish will not eat my coral and invertebrates?

    • You can never be 100% sure about the compatibility of your new fish until you release it into your aquarium and watch its behavior.
    • What you can do is educate yourself, make educated selections, and hope for the best. It is what all hobbyists must do.
    • Please note: Most fish that eat coral have only a few selected types of coral that they will eat and will not bother other corals. Read about the fish and corals on our website for more specific details about compatibility.
    • With corals, it is easy to remove them and trade with a friend.