Otocinclus
Otocinclus affinis are often called ottos. Ottos are small, suckermouth catfish that eat algae. Most come from Brazil. Unlike most other algae eating catfish, ottos will not usually eat your plants. They, in fact, clean algae off of plants (plecostomus are better at removing algae from the glass). Ottos grow to about 1.5 inches at most so they can live in small tanks (10+ gallons). Ottos are great fish for planted tanks with non-aggressive fish. They are very delicate and die easily. It isbest to get them in groups of at lest four. Usually some die but the survivors can live for years. See below for more information on keeping ottos alive.
Setup and Water Preferences
Ottos like slightly acid, soft water with lots and lots of plants. They prefer temperatures from about 22 to 28 degrees C. Even more than most fish, they need very clean, well-filtered water. Ottos should have driftwood on which to chew. They are very sensitive to medications. Otocinclus like swift currents in part of their tank. Ottos are reported to be nocturnal but most are active most of the time.
Feeding:
They eat soft algae as their predominant food, off of live and fake plants, ornaments, and other surfaces. For supplemental feeding, one can use algae tablets (made for plecostomus) with sprirulina and sometimes vegetables. Quarters of cucumber and squash or romaine lettuce can be fed but some aquarists report no luck. Some ottos will eat live or frozen small worms (white worms, tubifex), small brine shrimp, and insect larvae (mosquitoes or bloodworms). A healthy otto should have a continually full belly.