Marine Foods and Feeding

From Microcosm Aquarium Explorer


Poss's Scorpionfish eating a live cleaner shrimp. Scott W. Michael

The Art & Science of Getting Aquarium Fishes to Eat Properly
By Scott W. Michael
from The 101 Best Saltwater Fishes

Until the recent past, the unique nutritional requirements of captive seawater fishes was often overlooked by hobbyists. People tried to get by using foods meant for freshwater aquarium species, flake foods of terrestrial origin and frozen brine shrimp of questionable quality.

Fortunately, all this is changing. We now know that marine fishes need a diet primarily of marine origin. We recognize that a poor diet can equate to general ill health and greater susceptibility to pathogens. Some commonly observed problems with poorly fed marine fish include lateral line and fin erosion, weight loss, color infidelity, listlessness and disease outbreaks.

The modern day marine fishkeeper now has access to many great foods. One excellent staple is fresh and frozen seafood meant for the family dinner table. Shrimp, clams, squid and marine fish flesh, rinsed and finely chopped are fine foods with the balance of nutrients a marine fish needs.


Grate Your Own Rations

You can take frozen “green” shrimp, squid or marine fish flesh and run it over a cheese grater to produce nice, bite-sized shavings for your fish. Many graters have holes of varying size so you can adjust the size of the shavings to suit the size of the fishes you are feeding. If feeding marine fish flesh, avoid fatty species such as salmon, tuna, and herring, as they will leave an oily film on the water's surface.

Also beware that fresh foods can quickly spoil, polluting the aquarium. It is important to remove uneaten pieces from the aquarium bottom and the filter soon after the feeding session. (Better yet, never feed more than your fishes will eat up within five minutes or less.) Although some writers have suggested that feeding fresh or frozen seafood can spread pathogens to aquarium fish, this is a rare event. Good quality seafoods should pose no greater risk than any other rations.

Marine Aquarium Preparations

Frozen preparations specially formulated for marine aquarium species offer great convenience and are a wonderful staple food for marine fishes. Some of these are made up specifically for fishes of the various feeding guilds (e.g., carnivore diet, herbivore diet) or even specific taxonomic groups. One manufacturer has a specific formula for angelfishes (which includes sponge fragments), a diet for triggerfishes and also one for small sharks. Most of these frozen preparations consist of a mix of marine proteins (scallop, fish, crustacean flesh), supplemented with pigments, vitamins and essential amino acids. Look for chlorophyll-rich green preparations for herbivores and reddish cubes created for carnivores.

Frozen mysid shrimp are a wonderful “newer” food for marine fishes. Many species that normally can be difficult to feed will accept these succulent little crustaceans with gusto. They are also a nutritious food, relatively high in protein and fats. For example, the combined crude fat and protein content of mysid shrimp is approximately 72 percent, while in brine shrimp it is around 6 percent. Unfortunately, not all frozen mysid shrimp are created equal. Some brands tend to consist of mushy, mysid fragments rather than nice, firm, whole little shrimp.

There is one downside to feeding mysids. They are not high in carotenoids, so if you feed mysids exclusively, certain fish species may exhibit color loss. I recommend supplementing a mysid-heavy diet with some of the frozen preparations or flake foods with added pigments or so-called color enhancers.

Another new and highly nutritious food that is making its way into more and more aquarium stores is Cyclop-eeze®. This is a bright reddish-orange frozen bar composed of a tiny, bioengineered crustacean from the genus Cyclops. This is a food with lots of desirable HUFAs (highly unsaturated fatty acids) and high protein content. It has a very small particle size, it remains in suspension longer, and fish love it. Cyclo-eeze is especially good for small, zooplankton-eating fishes. It drifts around in the water longer than most foods and gives the planktivores time to pick the food particles out of the water column. When feeding this food, be aware that a very small chunk contains a lot of individual Cyclops—it is easy to overfeed. A dried form is also available.

Color Enhancers

Like most aquarists, I do feed some frozen brine shrimp and krill, but would never recommend you use them exclusively. Both of these traditional foods, and many other marine crustaceans, are rich in carotenoid pigments and do help fish retain their bright colors. Another way to ensure your fish are getting their nutritional "fix" is to soak fish food in an enhancer such as Selcon®. This contains omega-3 fatty acids and a stabilized form of Vitamin C, vital nutrients that are often missing in aquarium fish diets. It works particularly well if you are feeding freeze-dried foods, like krill, which soak it up like a sponge. When buying frozen brine shrimp, look for the premium, enriched brands.

Flake foods have also come a long way in recent years. There are some wonderful, nutrient-rich flake foods on the market today that are not only good for your fish, but can help maintain their amazing colors. Look for pigment-enhancing rations that will help reduce the likelihood that a spectacular fish will change from dramatic to dull on an ordinary aquarium diet. Certain flake foods target the nutritional needs of carnivores or herbivores, and new choices are constantly being introduced. Look for the best foods at local aquarium retailers that cater to demanding marine hobbyists.

Pelletized foods and tablet foods vary in their nutritional contents and not all fish are keen to ingest these hardened formulations. With the convenience of dried foods it is easy to offer your fishes more frequent feedings between meals of fresh or frozen rations.

Herbivore Choices

If you are keeping plant-eating fishes in your home aquarium, you will need to include vegetable matter in their diets. Many aquarists feed their herbivores romaine lettuce, spinach leaves and/or broccoli heads. Freeze or steam the leaf before introducing it into the aquarium to make it easier for the fish to digest these fibrous foods. There are a number of plastic clips with hangers or suction cups on the market that you stick or hang on the inside of the aquarium. This makes it easier for the fish to browse on the vegetable matter. Some aquarists take a piece of coral rubble, attach a leaf to it with a rubber band and drop it to the bottom of the aquarium.

An even better supplement for marine herbivores are the sheets, flakes or chunks of dried macroalgae that are now on the market. Not too long ago, this type of food product was only available to aquarists that had an Asian food market at their disposal. (Nori is dried algae used in the preparation of sushi and now available at many supermarkets.)

Dried algae specifically made for aquarium feeding is now available at many aquarium stores. These products are available in sheets or in chopped up pieces, and they enable the aquarist to feed their herbivores brown, green, and red algae species. You should feed these to your herbivores on a daily basis. Offering a variety of different herbivore foods is the best approach in most cases.

Live Foods

Live foods will be eaten greedily by most aquarium fishes, and they can be used to supplement your fishes’ diet or to help induce a fastidious fish to feed. (Those interested in breeding marine fishes know that live foods can be crucial in conditioning broodstock and stimulating spawning behaviors.)

Live brine shrimp and ghost shrimp are a favorite of many marine fishes. It is a good idea to enrich or gut-pack them before feeding them to your fish. Place an enriching supplement such as Selcon, a finely ground, nutritious flake food or Cyclop-eeze in with your live shrimp an hour or more before feeding them to your marine fish.

Freshwater crayfish and fiddler crabs are great treats for predators big enough to take large crustaceans. Freshwater livebearing fish such as mollies and guppies are popular foods but lack the fatty acids that marine fishes need for good health. You can also gut-pack these feeder fish before presenting them to your captive charges, but never rely on them as a regular part of your marine fishes’ diet.

Live marine clams or mussels, often available in the seafood section of grocery stores or in fresh fish shops, are a great food. These mollusks are particularly valuable for enticing picky eaters, like certain butterflyfishes and angelfishes, to start feeding. Simply break the shell open with a screw driver and a hammer and then throw the open clam into the tank. The feeding frenzy that ensues is remarkable.

Feeding Frequency

The amount and frequency of feeding for any particular aquarium will vary to suit the fishes being kept. For our purposes, we can break reef fishes down into three general feeding groups: the herbivores, the carnivores, and the omnivores. (Additionally, zooplanktivores are open-water carnivores.)

Many community tanks have a mix of these different fishes, and the best way to ensure that all their nutritional prerequisites are met is to rely on a varied diet. This means a combination of flake, frozen and fresh foods. Relatively few reef fishes are specialized feeders. For example, the vast majority of carnivores feed on a number of different types of prey, not just a single animal species. With your reef fish, variety is essential to ensure their long-term health. The herbivores feed mainly—but not always exclusively—on plant material, and they tend to consume large quantities of food. For example, the Cortez Gregory (Stegastes rectifraenum) takes over 3,000 bites in a day’s time, and it needs more than 500 bites to fill its gut once. This fish, which reaches a maximum weight of about 2.5 oz (70 gm), consumes about 0.4 oz (11 gm) of algae per day—or approximately 16 percent of its total body weight per day. The human equivalent would be 27 pounds of food for a 170-pound male or 19 pounds for a 120-pound woman. Herbivores have to consume large quantities of food because algae contains a limited quantity of digestible nutrients and they also have to expend considerable energy in their grazing activities.

When keeping herbivores, you should bear these facts in mind, especially if your aquarium is devoid of algae. Rather than giving them one big meal daily, it is best to provide several smaller feedings throughout the day. To supplement this, you can add a piece of dried algae to the aquarium once a day. If your herbivores quickly eat the algae add another— just remember to remove any uneaten pieces after 12 hours or before you go to bed. I have seen sickly, emaciated tangs become healthy and fat as pregnant cows using this feeding technique.

For anyone keeping a fish-only aquarium, I strongly suggest that you encourage a lush growth of filamentous algae, which will act as a natural food source for these fish. Some of the healthiest captive tang (surgeonfish) I have ever seen have been in tanks with a thick mat of green hair algae on the back glass and rocky substrates. If you have a reef aquarium, or a fish-only tank, the occasional introduction of Caulerpa or red macroalgae will be appreciated by browsing fish species.

Meaty Meal Times

Carnivores are the most well-represented fishes on coral reefs. They vary greatly in the types of food they ingest and their hunting techniques. Those groups that feed on encrusting invertebrates (angelfishes, butterflyfishes, filefishes, triggerfishes, puffers and others) are well-known for grazing actively throughout the day. For example, the French Angelfish (Pomacanthus paru), which feeds mainly on sponges in the wild, takes an average of about three bites per minute during daylight hours. Like herbivores, these species need to be fed several small meals during the day rather than one large feast.

Carnivores that hunt small benthic invertebrates also feed often. These species (many dottybacks, cardinalfishes, wrasses, dragonets, gobies) should be fed at least a couple of times per day unless their normal fare is present in appreciable quantities in the tank—usually small crustaceans living and breeding in the live rock or patches of macroalgae.

Larger, predatory fishes—such as morays, lionfishes, and groupers—that feed on bigger prey items usually ingest a sizable prey item once a day. Some even feed less frequently than this (e.g., several times a week). Zooplankton feeders (anthias, fairy wrasse, flasher wrasses, dartfishes) are well-suited for the home aquarium because of their natural feeding behavior.

Aquarists typically introduce food at the water's surface and the fish feed on it as it sinks through the water or as it is blown about the tank by water pumps. This feeding situation is very much like that normally encountered by zooplankton feeders in the wild; that is, they pick moving food out of the water column. It is very important that active zooplanktivores are fed more frequently than most other carnivores. It is best to feed them at least three times a day.

From: The 101 Best Saltwater Fishes