When deciding on fish for your saltwater aquarium, the species you choose should be compatible in size, attitude, and dietary needs. After all, your saltwater fish will be living in the confined space of an aquarium.
- Size: One aspect of choosing fish that you might overlook is the maximum size of a particular species. A fish grows continuously throughout its life, and some species grow faster than others. You don't want a fish that will grow to 12 inches in less than a year. This situation not only will disrupt your aquarium capacity, but the larger fish undoubtedly will dominate the tank. Some species are compatible with other species when they are smaller juveniles but become solitary and aggressive as adults. These fish don't belong in the peaceful reef tank (an invertebrate aquarium with a few peaceful fishes) or fish-only tank.
- In the wild, bigger fish usually eat smaller fish and invertebrates. This phenomenon also will happen in your aquarium, and it's just one more reason to keep large fishes out of the average aquarium. Keep fishes of similar size in your fish-only and reef aquariums.
- Attitude: Some fish species have a surly disposition. Whether it's because they're territorial, defensive, or just plain hungry, these fish are not for the reef tank and don't fit into most peaceful fish-only aquariums.
- In general, avoid aggressive fishes. Note that "normally aggressive" doesn't mean that your fish will be docile. Many species that are considered peaceful have been known to have a few bad seeds. Take the time to discuss your options with your dealer and keep a watchful eye on any new tank addition. If one of his fish is aggressive, the dealer should tell you (at least you hope he will), or you will undoubtedly find out one way or another. This is a good reason to establish a good rapport with a dealer.
- Diet: In addition to size and attitude, always consider the diet of your tank inhabitants. Fish definitely have a variety of food preferences. Be wary of predatory fish, called carnivores, because they eat other fish and invertebrates.
- Avoid adding large predators to your reef tank or fish-only tank: It's a bad mix (at least for the prey). In addition, don't choose fish that are going to be difficult to feed. For example, it's hard to feed fish with specialized diets, like those that eat only corals. Always consult with your dealer.
