My local fish shop only has otocinclus affinis, are they suitable for my tank?
The identification of the specific species of oto in the home aquarium is not always easy as there are several with very similar patterns and the names attached to them in stores are frequently inaccurate. Fortunately the care and behaviour is basically identical whichever species you may have in your aquarium. No
Otocinclus species possesses an adipose fin, but this fin is present on the species in the closely-related
Paratocinclus genus.
Otocinclus macrospilus is probably the species most often encountered in the hobby; this species is often mis-identified as
O. affinis [see comments below]. It is strikingly similar to
O. vestitus and can be distinguished by the markings on the caudal (tail) fin.
O. macrospilus has a dinstinctive large round black blotch at the base of the caudal fin; on
O. vestitus the horizontal black band extends onto the caudal fin with no significant enlargement into a blotch.
O. vittatus is another near-identical species, but the upper edge of the black horizontal band along the sides of the fish is bordered by a distinct white clear band separating the black band from the mottled pattern; on
O. macrospilus the white band is less distinct in places and on
O. vestitus the mottled pattern adjoins the black band with no definable white band.
This is a shoaling fish that will usually not last long if acquired on its own or even as a pair; a group of three minimum is required, more when space allows; you could have five, but please note what follows.
The aquarium should be well-planted; this species' sole activity during daylight hours is to graze algae from plant leaves, wood, rock, tank walls--indeed any surface. It will frequently stop to rest on the leaves of plants, and may frequently be inconspicuous in the aquarium. Without abundant plants and other surfaces it will feel exposed and vulnerable and such stress readily brings on health issues and early demise. There have been reports of otos feeding off the sides of certain other fish; this habit is probably the result of stress or insufficient vegetable (algae) matter in the aquarium. Otos continually eat, so this must be considered when acquiring them.
There is a high mortality rate among newly-purchased otos. This is because they are wild-caught, and upon arrival in stores are most often nearly starved; being an algae-eater, it needs regular feedings of such food. They should always only be introduced to a tank containing plants with algae [this replicates their natural habitat], either the common green algae or diatoms (brown)--these fish will not eat algae such as brush, beard, etc. If this is not done, they may very likely starve to death quickly. Once they have eaten algae and settled in, usually after several weeks, they will quite readily find and eat sinking algae-type discs and tablets, along with fresh vegetables. But initially algae must be present or death usually occurs within a couple days to weeks.
One method that can work is to use dried leaves; oak, maple, beech are all safe (as leaves), and can be collected after they have fallen from the tree in the autumn. [You can purchase Indian Almond Leaves in some fish stores.] Choose a safe collecting site, away from any chemicals, pollutants, fertilizers, pesticides, etc. I have an oak tree in my back garden and every autumn I collect a large bag of fallen oak leaves, lay them out on paper towels to dry, then bag them. Placed in the aquarium, it takes a couple days for the leaves to become water logged, after which they sink and can be laid on the substrate or placed upright among plants or chunks of wood. All grazing fish will readily (usually) feed off leaves, as it is a natural component of almost every tropical habitat. The infusoria produced is excellent food for all fry too.
