Nathan's MITy Aquarium

Species	Otocinclus species AKA "Oto cats"
Photos	Mmmm... beans! There are two species of Otocinclus in my tank, the smaller (or juvenile), lighter colored one sitting on the bean, and the darker, spotted, and more rounded ones. Underside. Being wary of puffer. Top. Camoflaged on a rock. Top & side. Sitting on an anubias.
Diet	I bought the Otos because they are highly spoken of among enthusiasts as what i would call good algae control experts (ACEs). They remain very small, and won't eat plants. Two months after i set up my new tank, the brown algae was making it pretty unsightly, covering the sides of the tank and the gravel, as well as the leaves of the plants. In desperation, i bought the only two otos the closer LFS (local fish store) had one day. They went to work on the algae, but didn't make much progress. Then one died, so i went to my preferred, but farther removed, LFS and bought four more to keep him company. These Otos were larger, darker, more teardrop shaped, and spotted. The platoon of hungry otos immediately began maneuvers, and within a week the tank looked sparkling clean. Now the problem was "What to feed the otos?" Knowing that their cousins the bristlenose plecos love canned green beans, i bought a can of french cut beans and dropped some in. The beans gradually disappeared, but not nearly as rapidly as the newest plant in the tank. The hungry otos decided that they'd go on a plant-eating strike, earning the dubious distinction of rare plant-eating otos. So much for common knowledge. Time will tell if they accept my settlement of beans, or put the plant out of commission... permanently!
Behavior	Many if not all otos are described as shoaling fish: they are much more comfortable in groups. I observed this behavior with the first two otos i bought. When a puffer would get too close, the smaller (surviving) oto would often try to swim close behind one of the danios in the tank, which are of a similar size and coloring. The danio was never sure what to make of this funny-looking fish stalking him. The comical result of this was a small oto cat "chasing" around a sleek danio. Eventually, the oto would come to rest again, settling back down into his favorite position (poised motionless on a leaf). The other otos seem to prefer hard, vertical surfaces like the sides of the tank and stones. They'll hang out together like aquatic bats, stuck to the side of the tank up in the corner. Otos have a reputation for being delicate when they are first added to a tank. For no well understood reason, a few will not make it more than a week, but those that do typically live out a long life. I've lost one oto from each batch i purchased (1 of 2, 1 of 4), and i know that the second batch were well adjusted to the LFS tanks before i brought them home, so i don't think it's just transport stress. 20030131 update: Another oto disappeared over Christmas break, but the three remaining seem to be doing well. They like to hang out on the driftwood i added, and the dark coloration lets them blend in very well.
Links	Further information can be found on Planet Catfish, under Otocinclus. The aquarium main page