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You've been careful to keep your fish tank clean and feed your finny friends small amounts of food on a regular basis, but all of a sudden you realize there's algae growth in your tank. Algae thrive on the food your fish inevitably miss and no filtration system exists that can collect all the particles of food and waste in the tank. What's a pet owner to do?

One solution is to introduce scavengers to help clean up your tank, but introducing scavengers has to be undertaken carefully or you may end up with a solution that's worse than the original problem.

Algae 101

Most people think of algae as a plant, but it actually shares characteristics with bacteria as well as plants. Like bacteria, algae reproduce by cell division or the production of spores. Algae act like plants in contributing to the nitrogen cycle through the use of photosynthesis, which changes carbon dioxide into oxygen and causes fluctuations in the organisms' pH and oxygen levels.

There are over 25,000 known species of fresh and saltwater algae and probably a lot more waiting to be discovered. Algae can be single-celled organisms invisible to the naked eye or can form multi-celled colonies that can grow up to 164 feet long and resemble seaweed. All forms of algae are an important part of the aquatic food chain. There are five basic groups of algae, some harmless and others capable of introducing toxins into your aquarium.

Green Algae inhabit marine and fresh water environments and can be single-celled or filamentous weed and seaweed. In an aquarium, algae can cause green water, which can only be countered by making a major water change.

Yellow-Green Algae and diatoms live primarily in freshwater but have been found in saltwater, damp water and tree trunks. This group creates fine hair growths over your rocks, decorations and plants.

Blue-Green Algae are found almost anywhere including on land, in the water and even in the air. This group is the most primitive and dangerous type of algae because it is the most closely related to bacteria. Some species are capable of introducing highly poisonous toxins into your water. Blue-green algae aren't always blue-green. Sometimes they're blackish, greenish, brownish or reddish.

Red Algae are an attractive marine group that ranges from small single-celled organisms to large branching seaweed.

Brown Algae are another mostly marine group that's more common in cooler water and includes large seaweed-like kelps and wracks. It's important to make sure your aquarium doesn't have too much of the wrong type of algae, but it's also to important to maintain balance because some types of algae can add valuable micronutrients to your fish's diet. One easy way to maintain this balance is to introduce algae feeders into your fish tank.


There are a wide variety of freshwater and saltwater scavengers available including fish, snails and shrimp, to help rid your tank of excess algae. It's important to choose carefully because some of these scavengers are more trouble than they are worth.

Freshwater Scavengers and Algae-Eating Fish

Chinese Algae Eaters are well adapted for scraping algae from flat surfaces because they are sucker-mouthed bottom feeders.

Cory Catfish are a peaceful bottom-dwelling scavenger that helps clean waste from the tank. They are best kept in groups with other peaceful fish.

Loaches are traditionally recommended as scavengers, but not all species are suitable for this role and some have to be fed just like other fish. Effective scavengers include coolie loaches, dojo loaches, dwarf loaches and sucker loaches. One caveat about sucker loaches is that when mature, they can nip other fish and may latch onto flat-bodied tank mates in the absence of algae.

Pictus Catfish (or Antenna Catfish) does best in a tank with plants, rocks and driftwood. Keep them in groups of three or more with other peaceful fish.

Redfin Prochilodus will add color to the tank and help with algae control. They are best kept with peaceful fish of similar size.

Plecostomus Catfish are more commonly known as Plecos and are included in the 70 species of sucker-mouthed catfish. Plecos are probably the most popular of the catfish species. These fish are such dedicated algae eaters that you'll have to supplement their diet with vegetable flakes.

Freshwater Shrimp

Bamboo Shrimp are a community fish equipped with brushes on their limbs that act as traps for filtering food.

Long-armed Prawns can grow rather large, up to 6 inches. They are scavengers of algae and debris, and are best kept with larger fish. Avoid grouping with long-finned fish.

A color variation of the Crayfish, Blue Crayfish are great scavengers to help keep a tank clean. They are best kept one per tank with large, fast fish.

Freshwater Snails

It's not a good idea to deliberately introduce snails into your tank because they'll make a meal of your plants before they even notice your algae. However, you'll probably end up with them anyway because snail eggs sometimes come attached to purchased plants. If you need to get rid of small snails, clown and skunk loaches are among the more efficient snail-eating fish. Some larger snails, such as the golf-ball-sized apple snail or black mystery snail, may be an attractive addition to your aquarium. Do not house snails with cichlids, turtles or puffers.

Saltwater Fish

Butterflyfish do eat algae, but they also require a mixed diet so they cannot be relied upon to clean your tank.

Surgeons and Tangs both thrive on algae colonies but if no algae are available, you'll need to feed them vegetable-based foods to supplement their diet.

Wrasse and Hogfish in their juvenile stage will act as cleaner fish by picking parasites from their neighbors' scales.

Blenny of several species, particularly the bicolor blenny, browse the bottom for algae.

Goby are bottom-dwelling carnivores that often live in harmony with shrimp. Gobies cannot, however, compete with most fish for food and must be kept in a mature reef system.


Hermit Crabs are scavengers who'll also clean up waste food. It's also important to provide your hermits with larger shells to move into when they outgrow their original homes.

Fiddler Crags can be kept singly or in groups. This scavenger will help keep your tank tidy by cleaning up waste.

Sally Lightfoot Crabs eat bubble and hair algae. They're also very shy and may hide in your tank until they get used to their new environment. They are best housed with larger fish.

Arrow Crabs are excellent scavengers. Keep only one per tank and do not mix with other crabs, shrimp or small/medium fish.

Saltwater Shrimp

Coral Banded are cleaner shrimp that are notorious scavengers. They use their long antennae to 'advertise' their cleaning services. They're known to be aggressive toward very small fish and other shrimp species. It's a good idea to keep only one.

Red or Fire Shrimp are good scavengers who'll eat almost anything that's offered. They are also used occasionally for parasite control because they eat the protozoan that's responsible for Ich. They are best kept singly with larger fish.

Cleaner Shrimp clean organisms off your fish. They are best kept in groups with community fish.

Saltwater Snails

Turbo Snails grow up to three inches, and they will browse the surface of your glass in search of algae. They work wonders cleaning your aquarium glass, but they're not very good at cleaning rough surfaces. There are many different species of turbo from which to choose.

Other Saltwater Scavengers

Sea Urchins live principally on algae and some species, such as the pink pincushion urchin, make much better aquarium inhabitants than others. If you're thinking about adding a sea urchin to your aquarium, do your research carefully because some species have venomous spines and can inflict a nasty sting. Another thing to consider is that sea urchins are a favorite meal of the triggerfish.

Starfishes and Brittle Stars can be good choices for your aquarium because they're algae eaters who also browse the bottom looking for scraps of missed food. It's important to research your choice carefully because some species have been known to eat sleeping fish or attack other invertebrates.

If your tank is looking a little dingy and you don't want to add chemicals, you might want to consider adding some scavengers to help clean up the algae and to add a little color to your underwater world.