What Kind of Marine Fish Will Eat Algae?

Rabbitfishes are excellent algae-eaters on the reef and in a saltwater aquarium.
Rabbitfishes are excellent algae-eaters on the reef and in a saltwater aquarium. (Image: Jupiterimages/Photos.com/Getty Images)

Unsightly algae growth is a common problem for saltwater aquarists. One way to prevent a so-called algae bloom in a new marine aquarium, or address nuisance algae in an established aquarium, is to add compatible algae-eating (herbivorous) fishes. Not all algae-eating fishes are suitable in all aquariums, so it is important to consider the specific aquarium in which the fish will be housed, as well as that fish's long-term husbandry requirements.

Algae-Eating Fishes for a New Saltwater Aquarium

New marine aquarists often become discouraged by uncontrollable algae growth in a new saltwater aquarium. When establishing any new aquarium, it is important to spend adequate time planning before purchasing equipment and fishes, as this will help avoid many common beginner problems like unattractive nuisance algae. By choosing a few compatible fishes that are known algae-grazers, you can keep algae growth in your new aquarium in check. Some of the best choices, depending on tank size and compatibility, include tangs, rabbitfishes, angelfishes, blennies and gobies.

Algae-Eating Fishes for an Existing Saltwater Aquarium

Adding algae-eating fishes to an existing aquarium is a way to deal with a sudden algae outbreak, so long as you also address the underlying cause and take into account the future nutritional needs of the fish. Introducing any new fish to an established aquarium has its risks. Aggression issues are often more severe in an established aquarium, and from an animal health perspective, you do not want to acquire an animal that will suffer from malnourishment once the nuisance algae is under control.

Proven Algae-Eating Fishes by Tank Size

Each aquarium is different, and adding any fish requires fully understanding the animal’s needs, along with any compatibility issues. One of the most critical constraints beyond compatibility is recommended tank size, keeping in mind that juvenile fish will grow larger over time.

In larger aquariums of at least 125 gallons, consider rabbitfishes from the genus Siganus for effective algae control. The scribbled, foxface and magnificent rabbitfishes are all good choices. In an aquarium of at least 75 gallons, you might also consider some tangs from the genera Ctenochaetus and Zebrasoma. In particular, kole, chevron, sailfin, bristletooth and yellow tangs are aquarium favorites when it comes to algae-eating prowess.

While rabbitfishes and tangs may grow too large for smaller tanks, there are many algae-eating fishes you can keep in smaller systems. A few dwarf angelfishes from the genus Centropyge are good herbivores for an aquarium of at least 50 gallons. Consider both the lemonpeel and flame dwarf angels. Blennies from the genus Salarias are excellent for algae control, and the most popular one, the lawnmower blenny, can be kept in an aquarium as small as 30 gallons. When it comes to even smaller tanks, there are several gobies from the genus Amblygobius, like the attractive Rainfords goby, that are good at helping to control algae.

Feeding Supplemental Algae

Most marine fishes are omnivores, meaning they will consume both plants and animals, and many fishes will readily accept a diet of commercially available foods. Nonetheless, some fishes require a sufficient supply of herbivore-specific food in order to maintain good health. A saltwater aquarium that is “too clean” can be a problem for fishes that spend their days grazing on algae, and it is usually best to supplement these fishes’ diets with an appropriate substitute specifically formulated for herbivores, such as a dried seaweed product or a flake, pellet or frozen food with spirulina. Live macroalgae can also serve as a welcome treat.

Many marine herbivores will require supplemental feedings of herbivorous foods.
Many marine herbivores will require supplemental feedings of herbivorous foods. (Image: Comstock/Comstock/Getty Images)

Other Considerations

While employing algae-eating fishes is a good way to control nuisance algae growth, you must also address the underlying causes of excessive algae. Most commonly, the sources of unwanted algae are a combination of too many fishes, overfeeding, poor source water quality, deferred filter maintenance and too much light. Addressing theses issues will help prevent future algae problems. In addition, utilizing a so-called “clean-up crew” of herbivorous invertebrates, like various snails and crabs, is considered standard practice by many saltwater aquarists.

Also consider algae-eating invertebrates, such as snails, to control nuisance algae.
Also consider algae-eating invertebrates, such as snails, to control nuisance algae. (Image: Jupiterimages/Photos.com/Getty Images)

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