Providing your fish with the right type of food in the right proportions is a very important task. This can be much more of a challenge in a saltwater tank than in a freshwater tank, because most marine fish are still wild-caught, and their natural diet can be difficult to maintain in captivity. With the right information, however, most marine fish will learn to eagerly anticipate their feeding time and will voraciously devour their food.
A good rule of thumb to follow is that fish should be fed no more than they can consume within a five minute period. Any food that is left behind after feeding time should be removed before it has a chance to begin decomposing. If you find that your fish are consuming the food in far shorter a time than five minutes and seem anxious for more, you may need to increase the amount you are feeding them. On the other hand, if your fish are healthy, but they are only consuming about half of what you’re feeding them, you will probably need to start feeding less. Always keep in mind that much more harm can be done to your fish by overfeeding than by underfeeding.
In the wild, reef fishes will browse for food throughout the day. Since you should be attempting to mimic their natural habitat as closely as possible, it is recommended that you feed your fish several small meals every day. At the very least, feed two medium-sized meals per day, one in the morning and one at night.
The kind of food to feed depends on the kind of fish you’re feeding: herbivore, carnivore, or omnivore.
It is common for fish that graze on algae in the wild to suffer in captivity because they don’t receive the appropriate type of food to keep them healthy. Many of these fish (tangs and angelfish, for example) are fed terrestrial greens like spinach and romaine lettuce, but these are not appropriate foods for these fish that are solely algae eaters. They should be fed either dried or fresh algae. Dried algae is sold in paper-thin sheets that can be broken down into appropriate portion sizes, depending on the number of fish you are feeding. Fresh algae can be obtained by placing a glass container, with one rock from your aquarium in it, on a sunny windowsill. Wait for the rock to grow a nice layer of algae, and then place it back in the aquarium for your fish to graze on.
Herbivorous fish can also be fed one of the frozen fish foods that is formulated especially for herbivores. This food should contain a variety of marine algae, vegetable matter, and seafood. Whether you feed your herbivorous fish dried algae, fresh algae, or a frozen food formula, herbivorous eaters are grazers and should have food available to them at all times, unlike most other fish. You should replace their portions (and remove any old, eaten algae) once every day.
Meat-eating marine fish can enjoy a variety of fresh, frozen, freeze-dried, and live foods. Fresh foods suitable for your fish include many seafood items, such as shrimp, scallops, mussels, clams, and some fish. If you’re serving seafood to your fish, cut it into bite-sized pieces (or serve it whole to larger fish). Fresh seafood can be frozen and then thawed as needed.
Frozen foods are available from most fish shops and other sources. These offerings may include brine shrimp, bloodworms, and daphnia. They may be in the form of a slab that can be broken into smaller pieces or small, ready-to-go cubes. To feed frozen foods to your carnivorous fish, thaw a small portion in aquarium water, and then drop it in the tank.
Several freeze-dried foods for carnivorous fish are readily available, such as plankton, krill, brine shrimp, and bloodworms. Freeze-dried foods are foods that have been completely dehydrated, yet they maintain most of their nutritional value. They have a relatively long shelf life, particularly when compared to fresh and frozen foods. Freeze-dried foods should be used as supplements for carnivorous fish.
Live foods are almost always a favorite of fish. Adult brine shrimp, bloodworms, and Mysis shrimp are among the better choices. Earthworms are also a great live food choice because they come in all sizes, fish love them, and you can collect them right from your own garden. Be sure to thoroughly rinse them before feeding them to your fish.
The majority of marine fish are omnivorous, which means they need to eat both meat- and plant-based foods. One easy option for omnivorous eaters is commercial fish food, such as flakes or pellets. However, offering a varied diet will give you healthier, more colorful fish. Try feeding your fish two feedings a day of commercial fish food and one feeding of a meaty item, such as bloodworms or chopped fish. Try to keep alternating the food you offer in addition to commercial food to keep the fish from getting bored and to make sure all of their nutritional needs are met.