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11:08 PM   March 28, 2015
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Nuisance Algae and Fish That Eat Them

Some fish have great appetites for the green stuff; others cause more problems.
By David Lass

Royal farlowellas (Courtesy of David Lass)

Retailers know that every hobbyist will experience problems with algae at least once. The extent to which this is bothersome depends on whether the algae take the form of green slime, green water or growth on surfaces of the aquarium. Some fish that eat algae are better at it than others.
Nuisance Algae
The  green slime algae can cover everything in the tank. This is actually a cyanobacteria (between a plant and a bacterium), and it comes from too much light and too much fish food (i.e., phosphate). Tank owners can often eliminate cyanobacteria by lowering light levels and cutting back on food. In difficult situations, treating the entire tank with an antibiotic or tearing down the tank and starting over are required.

Green water, the next most difficult algae problem to deal with, comes from too much light and too much food and can often be fixed by cutting down on both and leaving the tank in total darkness for a few days. Running an ultraviolet sterilizer on the tank can eliminate green water quickly, as it kills the algae spores that are floating in the water column.

The most common form of algae grows on any of the surfaces of the aquarium—the glass, filter and heater tubes, plants, rocks or ornaments. While this form of algae also comes from too much light and too much food, in reality it is usually present in varying degrees in any tank. A number of fish eat algae on surfaces in the tank. Some of these fish are excellent at what they do; others can cause more problems than they solve.
Good Algae Eaters

Pleco (Courtesy of David Lass)

In determining good algae eaters, the criteria for using the term “good” are that the fish must actually eat a fair amount of algae and it must also be a good community tank fish. Although opinions vary on the extent that certain fish make good algae eaters, the Siamese algae eater, Crossocheilus siamensis, is ranked near the top. Often the flying fox (Epalzeorhynchos kalopterus) is confused in the trade with the true SAE. An easy way to distinguish between these two is that the SAE has a broad black line extending all the way into the tail itself and no gold line at all. On flying foxes, the black line stops before the tail and a prominent gold stripe extends the whole length of the fish. Flying foxes are not good algae eaters; true SAEs are excellent ones.

The genus Otocinclus has a number of different species that are excellent algae eaters. The only problem occurs when they have eaten most of the algae and are looking for other things to eat. Otocinclus have reputations for being touchy fish to keep, but they need to be fed in addition to their eating algae. Spirulina wafers or pieces of blanched zucchini or potato are good options for these fish. Other fish will also snack on these, but it is imperative to offer these foods to Otocinclus, especially in tanks in the store. They will not survive on just the algae present in the tank.

A final group of good algae-eating fish is the smaller sucker-mouthed catfish, such as those from the genus Ancistrus. These fish can be distinguished from the larger “pleco” type catfish by their spiked extensions (called odontodes) that protrude from the side of their mouths and cheeks. The most common Ancistrus available in the hobby are the bristle-noses and the white spots, of which there are a number of different species. Ancistrus will eat algae and not grow too large. Other excellent algae eaters, but ones not seen all the time in the hobby, are fish from the genus Farlowella.
Common Algae Eaters That Aren’t

Algae and Fish Facts

  • Nuisance algae are common, especially for new hobbyists.
  • Retailers can tell aquarists that green slime algae and green water can be remedied with antibiotics, ultraviolet sterilization or cutting down on light and food.
  • Some fish can control algae growing on surfaces of a tank. True Siamese algae eaters, Otocinclus, Ancistrus and Farlowella make excellent algae eaters.
  • Chinese algae eaters and common plecos, though inexpensive and readily available, are not good algae eaters and they grow too large for most tanks.
Although opinions can vary, two fish that are widely sold in the hobby as algae eaters really don’t eat much algae at all. These two fish are the Chinese algae eater, Gyrinocheilus aymonieri, and the common pleco (either Plecostomus or Hypostomus species). The CAE doesn’t really eat that much algae, especially as it grows, and it can become territorial. CAEs also commonly grow up to  8 inches in a tank.

The common pleco also does not live up to its billing as an algae eater, and this fish can easily grow to 12 inches or more—much too large for all but a few hobbyists to handle.

It does not take long for either of these fish to learn that every day, at roughly the same time, the Flake Food Fairy comes and drops good-tasting food into the tank. This food can be obtained at much less expenditure of effort than eating algae from surfaces in the tank, and soon these supposed algae eaters simply don’t eat algae. <HOME>

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