Algae are a real nuisance for every aquarium hobbyist. Even small disturbances in the ecosystem may cause algae to multiply at an alarming rate. It rapidly overgrows plants, reduces their ability to photosynthesize and considerably reduces the amount of oxygen, which in extreme cases can lead not only to the death of the plants, but even to the death of the fish! The algae also reduce the aesthetic value of the water, taking all the joy out of observing the underwater world. That is why many hobbyists, wanting to get rid of them as soon as possible, reach for specialist chemical preparations, but this should be the last resort. It is better to focus on preventive measures – maintaining good and stable water parameters, proper feeding and effective filtration. Fish that feed on algae can also be a remedy. Which of them are worth introducing to your tank?
Common carp (Loricariidae)
The common armyworm, commonly known as “whiskerfish”, belongs to a large group of freshwater catfishes. It is counted among the algae of the genus Loricariidae, of which there are about 70 species. Each of these species can be found in the wild from Panama (Latin America) to the Rio de la Plata basin in Argentina. They inhabit the rushing and still waters of the Amazon basin. During the rainy season common armyworms move to wet forest areas. They usually reach a size of 12 to 15 cm.
This species has a very characteristic body structure for armyworms – a flattened body with a wide head and two dorsal fins. The mouth ends in a special sucker that allows it to attach itself to various surfaces and scrape off algae. The common armadillo has no scales, as its skin is covered by bony plates that form a kind of armor.
The common armadillo is an extremely sociable fish, but it is very territorial towards other armadillos. Due to its gentle disposition it fits well into a social aquarium, while its easy adaptation to various conditions makes it recommended for beginners.
The tank for this algae should be relatively large and at least 60 cm long (armored fish kept in too small aquaria become dwarf – ed.). It is also worth taking care of proper, moderate water hardness, strong circulation and proper filtration. Stability of water parameters is crucial in this case. Ordinary sand or gravel can be used as a substrate. Furthermore, the aquarium should provide numerous hideaways such as small rock caves, ceramic pots or coconut shells. It is also necessary to place roots or pieces of wood that provide the armadillo with valuable dietary fiber.
As they are typically herbivorous fish, their diet should be rich in plant components. It is also possible to give various dry food with spirulina, varied with cooked carrots, cucumbers, or lettuce, and rarely food of animal origin.
The term “algaecide” is a bit misleading in the context of the common armamentarium, after all only quite young specimens feed on algae, whereas adults are occupied with “cleaning” the tank bottom.
Otis (Otocinclus vittatus)
Otocinclus vittatus, or popular otfish, is a genus of freshwater, sum-shaped fish belonging to the already mentioned large family of Loricariidae. It lives mostly in South American waters of Brazil, Peru, Venezuela and Colombia. It inhabits smaller streams and densely overgrown rivers with a stable current. It grows only to 4-5 cm long. It is distinguished by a dark stripe running almost all along its body, and a dark spot at the base of its tail. Similarly to other plecos the mouth of the otos is transformed into a sucker. It is also equipped with spines, so you have to be very careful while catching it.
Otocinclus also belong to the group-oriented and sociable fish. It is therefore advisable to keep at least 6-7 specimens in a tank of about 50 liters. The water should be soft to medium-hard and the temperature should be 23-30ºC. It is worth keeping in mind that these algae are very sensitive to water quality (nitrites, ammonia) and rapid changes and fluctuations of its parameters, therefore it is necessary to ensure good water aeration combined with frequent, though small, water changes. In an ideal tank for otos, lush vegetation covers a considerable part of the aquarium (with dominant role of broad-leaved plants) and hiding places are located in various nooks and crannies – these may be coconut shells, roots, rock caves. The substrate can be made of sand or fine gravel – this is the area where the otos will usually stay. It behaves neutrally towards other specimens, which makes it easy to keep and therefore worth recommending to beginner aquarists.
The main food of this species is of course algae. They readily consume everything that grows on glass and leaves but does not form threads or brushes. They are herbivorous, so you can feed them plant foods in flakes, tablets, and even lettuce and carrots.
Siamese grub / “lawnmower” (Crossocheilus oblongus)
The Siamese grouper is a species of freshwater fish in the carp family that is better known in the community as the “lawn mower”. It is native to Southeast Asia – mainly Indonesia and Thailand. In the wild it occupies the bottom zones of streams and rivers, although it is also sometimes found in river floodplains. Its body has silvery-white shades with a dark stripe running from the snout to the tail section. “Reaper” is often confused with a similar fish of the genus Epalzeorhynchos (the so-called false reaper, which feeds poorly on algae), but anatomically it is distinguished by a band extending also through the caudal fin. A distinctive feature of the Siamese bigeye is a pair of anterior whiskers. This fish is famous for eating filamentous algae of the genus Compsopogon (so-called kelp), which cover plants in areas of more rapid water flow, hence it is so eagerly kept in aquariums.
the “lawnmower” is a gregarious fish, so it should be surrounded by a group of several individuals of the same species. It needs a large tank no less than 120 cm long (it grows up to 12 cm itself). The bottom can be either sandy or gravel. The composition can be formed by roots, decorative stones and pieces of wood, but the basis is invariably dense vegetation. This species prefers strong water currents, frequent water changes and effective filtration. The recommended water parameters are a temperature of 24-26°C and a pH level of 6.5-7.0.
Siamese grubs like to move around a lot, although they are non-confrontational and friendly to their surroundings. What draws attention is their unusual way of choosing their favourite place in the tank – lying down on a leaf or a stone and observing the situation carefully. They are omnivorous, so their menu may include dry, frozen, live as well as meat or plant foods.
Featured photo: Steven Gosch / Flickr