South American Catfish

As with Cichlids, most of the catfish in the hobby from South America are from the Amazon River basin.  Two major groups are represented. The ancistrus group, commonly known as plecos, are sucker-mouthed catfish who are often sold as algae eaters. Unfortunately, pet stores don't always tell their customers that many of the cute little plecos they see stuck to the glass can grow to be as large as two feet. Because of this, many novice fishkeepers end up with plecos who rapidly grow out of their ten gallon aquarium and must be re-homed within months of their purchase. Luckily, there are Ancistrus species who don't get so ridiculously large. Bristlenose plecos in particular are a very popular choice for a smaller suckermouth. The smallest members of the family, Otocinclus catfish, are very popular as tiny algae eaters, but are also reputed to be very delicate in captivity.

The other group, Corydoras catfish, are small communal scavengers. They swarm around the substrate snuffling through it for lost bits of food. They don't eat algae the way plecos do, but they do cut down on the toxins that algae feeds on by removing discarded food from the tank before it can decay. Cories are generally kept in groups, and are much more active that way, feeling more secure with a school than they would alone.