Instructions
Choose saltwater fish species that are known to be compatible with each other to avoid fighting amongst the fish. Ask the dealer you are purchasing from which species will be most compatible with the fish already in your tank.
Watch the fish's behavior for several minutes before purchasing. Note its swimming ability and any discolorations on the fish. According to Gregory Skomal, author of "Saltwater Aquariums for Dummies," healthy fish are usually very active and have clear, acute features. Avoid purchasing dull-colored or sluggish fish.
Look at the body of the fish and determine if it has been feeding normally. Underfed fish typically have thin bodies and oversized heads. Do not purchase such fish, as they likely have an underlying problem or disease that could spread to your other fish.
Make sure the fish is the right size to live in your aquarium. Research the type of fish and its environmental needs to ensure your habitat is adequately equipped to provide a proper home for healthy growth. Ask the dealer about any environmental requirements for specific saltwater fish.
Talk with the dealer and find a fish that has spent its entire life in captivity. Fish bred in captivity can more easily acclimate to a new environment and will grow to suit the size of the aquarium. Never purchase saltwater fish from the wild, as they are much less likely to survive in an aquarium.
How to Select Saltwater Fish
Selecting saltwater fish is an important decision that can have a huge impact on the state of your aquarium. Research is vital to choosing the right fish to complement the species already living in your fish tank, as well as new fish for a new aquarium. George Blasiola writes in "The Saltwater Aquarium Handbook" that having a close, trusting relationship with the dealer and knowing how to identify healthy fish are necessary skills for selecting new saltwater fish.