Q. I try to keep my fish aquarium clean, but I heard that some freshwater aquarium fish can help by eating algae. What are good algae-eating fish?
A. At one time or another, an aquarist will wonder if there is some fish that will eat all the algae and keep the aquarium looking nice. If you are looking for such a fish, one of the worst choices you can make is to choose the fish commonly called the Chinese algae-eater, which is found in local fish stores. This fish will make some attempt to graze on algae when very young and hungry, but as it grows its tastes mature, with a decided preference for the slime coat on other fish. This makes it something of a nasty companion for its tankmates. (For more information on Chinese algae-eaters, see “FishKidz,” starting on page 18. — Eds) But there are some fish that can help consume algae.
Hungry mollies and other livebearers do a decent job of munching on some types of algae, such as beard algae, and they get along well with most other fish. They breed like bunnies, so putting them in your aquarium can be trading one problem for another.
- Flag fish (Jordanella floridae, aka the Florida flag fish or American flag fish) do a very good job of munching on algae. Unfortunately, their temperament is touchy, and some specimens can be downright nasty.
- Rosy barbs (Puntius conchonius) also have algae appetites and only a mild taste for aquatic plants. Mine only rarely chomp an Anubias leaf, a misdemeanor easily overlooked, given the rarity of this behavior.
- Small shrimp (about one-half to 1 1/4 inches) that live in freshwater, such as the Amano shrimp (Caridina japonica), are helpful omnivorous scavengers. Like Otocinclus, Amano shrimp work all day long, but it takes a small army for them to have much visible impact on algae. Two dozen in a 30-gallon aquarium is not too many.
- Siamese algae-eaters (Crossocheilus siamensis), not to be confused with Epalzeorhynchus species, do a good job of eating very fine, thin, threadlike algae, including beard and brush algae. Unfortunately, they do not discriminate between algae and thread-leaved plants or the new growth on moss.
All of the above will eat some of the algae they can get their mouths on but will not do much for the kind of algae that grow as spots or film on surfaces. However, there are suckermouth fish that can help with that.
Otos (e.g., Otocinclus spp.) are the subcompacts of the family Loricaridae. Add a half dozen of these to a planted aquarium, and you will have an army of the hardest working little fish you will ever see. Owing to their mild disposition, small size and tender grazing habits, they are the loricarid of choice in aquariums smaller than 30 gallons. And as loricarids go, these are cute, with their lack of “bony” plates and small size (about 1 1/2 inches when mature).
They prefer to hide as much as possible. I once resigned myself to the loss of a dozen otos that I had put into a 30-gallon aquarium several months previously. I thought the otos had died or perhaps were being snacked on by one of the tankmates that, behind my back, was less neighborly than when I was watching. For an unrelated reason, I had to empty and rebuild the aquarium. As I tore down the aquarium, removing all the aquatic plants and driftwood and the hiding places they offered, I found all of the otos. Imagine a dozen fish remaining out of sight for months in a 30-gallon aquarium.