You can grow a wide range of fish in an aquaponic system, from koi and goldfish to trout and large-mouthed bass. The fish you choose will depend on several factors, the main one being what you intend to do with the fish. Some fish are edible, and grown for cooking or further processing, like tilapia, catfish, carp, etc. Other fish are ornamental, and bred for their decorative features, goldfish and koi are popular choices. These are less expensive than their edible cousins, and are typically more resistant to diseases, and easier to maintain.
Where you are will also help you choose your aquaponic's fishy residents. Some fish are strictly regulated in certain areas, and may not be legal to grow where you are. Some fish are also naturally more available in certain places than others, depending on their native environment -- they'll typically prefer the temperatures and conditions of their hometown, and may be hard to get where you are. Fish vary in how difficult they are to grow and maintain, some are more sensitive, and will require more attentive and effortful maintenance. Other fish are tough and durable, making them more appropriate for beginners (like tilapia and koi for example).
