Biological Algae Control
Algae-eaters are important inclusions in just about all aquarium systems. The most common algae eaters are fish, often referred to as ‘suckerfish’ due to their sucking and rasping mouthparts. Algae eaters may also include various invertebrates such as snails and shrimp. In saltwater aquariums, the choice of algae-eaters is quite astounding and can even include crabs, urchins and sediment-sifting organisms.
The best choice of algae eater is dictated by the type of aquarium and the objectives of the hobbyist. Seldom is there an occasion where just one species of algae-eater is adequate for controlling all algae issues. No one species will be capable of eating all species of algae or living in all types of aquaria.
By far the most popular species for algae control in Australia is the common Bristlenose Catfish, Ancistrus dolichopterus. Like all members of the Loricariid group, the Bristlenose has a flattened, downward facing mouth, resembling a suction cap. This species is extremely hardy and will live comfortably in almost any pH. They are extremely effective at eating various surface algae such as Green Dust Algae and Diatoms. However, their mouth parts make them incapable at removing stringy algae or from reaching algae in cracks or on any other coarse surface. Unfortunately Bristlenose will eat certain plants, particularly Echinodorus and young Anubias leaves. They also grow reasonably large (10-15cm), making them generally unsuitable for serious planted aquaria.
Smaller relatives of the Bristlenose are much better suited to this purpose. The Otocinclus Catfish is a popular choice with aquatic plant enthusiasts, renowned for its tireless cleaning efforts and lack of destructive tendencies. Unfortunately the Otocinclus is not as forgiving of water quality issues and will not thrive in excessively alkaline water. It is also a dwarf species, topping out at around 5cm. This makes them unsuitable for aquariums containing large or aggressive species.
Another option are the Whiptail Catfish. A diverse group, these attractive catfish come in a range of shapes and sizes. Like the Bristlenose, they will eat a wide range of surface algae but will not touch string algae. Whiptails are generally more delicate than the Bristlenose and so are also unsuitable for keeping with large or aggressive species. They will however, leave most plants alone, making them preferable for algae control in a plant display tank.
Biological control of string algae can be achieved with a variety of species. Livebearers – in particular Mollies – will generally make short work of filamentous algae. Livebearers are generally not considered the preferable solution though, as they will often fill up on the flake or pellets fed to the rest of the aquarium, abandoning their work on the algae. They can also look a little gaudy and out-of-place in an elegant planted tank and will usually not thrive for long in acidic conditions either.
A better option for filamentous algae is the Siamese Flying Fox or Siamese Algae Eater (SAE), Crossochilus siamensis. Young specimens make fantastic cleaners, constantly moving over the aquarium in search of algae to graze on. They are particularly good at cleaning algae from plants, capable of pruning it right from the tips of even the finest leaves. Their main drawback though is their lazy habits in old age. In fact, SAE above around 6cm are virtually useless, preferring to gorge on fish food instead. They can also be moderately aggressive when older, though mostly amongst themselves and towards other similar-looking cyprinids. For these reasons, SAE need to be constantly replaced with juveniles as they grow.
Snails and shrimp can also be useful additions in the war on algae. Though not usually very effective on their own, snails and shrimp can be useful from removing algae from fine surfaces such as thin leaves and hard to reach place. Both will also eat detritus such as dead leaves, fish faeces and uneaten fish food. By removing detritus, snails and shrimp help minimise the organic compounds which go on to feed the algae.
The best snail for this purpose are Red Ramshorns. They are small and unobtrusive and will generally behave themselves in a planted aquarium. They have been known to sometimes chew leaves, however this generally will not become an issue if their population is kept to a minimum. Ironically, overfeeding your fish can trigger a boom in snail populations, which actually causes them to run out of algae and turn on your plants. Proper feeding, coupled with adequate filtration and water changes will prevent overpopulation. They can also be crushed and fed to your fish. Most fish will relish them. For this reason though, snails and shrimp are not suitable for many aquariums as they will become food for your fish. Most loaches, cichlids, gouramis and bettas are expert shrimp hunters and will quickly decimate them in an aquarium. Snails can be kept with a wider array of species but will usually be eradicated by any loaches or cichlids.
Most aquariums will need to adopt a number of these species in order to get full algae control. It is also worth noting in closing that no amount of biological control will ever be complete – algae eaters are only one tool in the overall arsenal required to defeat algae. If your algae problems persist, you will need to consider making adjustments to your fertiliser regime and/or correcting water quality issues. Even the most well-run aquarium will occasionally even call for chemical treatment of algae.