Most aquarists think that they need a scavenger for their community aquarium. Somehow, this scavenger will consume and remove all undesirable matter and algae from the aquarium. There are species that can assist in aquarium maintenance, but there are no magical fish that will do it all, alleviating the aquarist from doing regular water changes, gravel cleaning, etc.
Scavengers (I like to refer to them as “workers”) can be divided into those that assist in removing excess algae from the glass and rock, and those that remove uneaten food that has settled to the bottom. The most readily available catfishes are suckermouth armored catfishes (family Loricariidae). The mouth is perfectly adapted for feeding on algae growing on rocks and driftwood. There are several loricariids that are well-suited for the community aquarium.
Pleco (Hypostomus spp.).
Hypostomus species would probably be the most common Loricariids, in part due to the fact that they are inexpensive and incredibly hardy. Although they have the potential to attain a length of 24 inches in the wild, they rarely exceed 12 inches in an aquarium. They are efficient algae-eaters in the community aquarium, but supplement their diet with green vegetable matter, such as lettuce, blanched zucchini squash weighted to the bottom and sinking algae wafers, as well as small live or frozen foods. Although they make good community residents, they can disrupt live plants as they move about the aquarium. Preferred water conditions consist of a temperature ranging between 72 to 81 degrees Fahrenheit, a pH of 6.0 to 8.0 and water hardness up to 25 dH.
Dwarf suckermouth catfish (Otocinclus spp.).
These fish are perfect for the smaller community aquarium because they only attain a length of approximately 1.5 inches. Because of their size, a small school of these fish can easily be kept in a small community aquarium. Unlike the pleco, which has brief bursts of activity while foraging around the aquarium, Otocinclus species are constantly in motion, grazing on algae growing on the glass and aquatic plants. These species prefer slightly acidic to neutral (pH 6.0 to 7.5) water, a temperature between 70 and 79 degrees, and a water hardness of approximately 10 dH. Supplement what algae they may consume with small live, frozen or flake foods, as well as sinking algae wafers.
The second group of worker catfishes include those that consume the uneaten food from the community aquarium. These are the smooth-armored catfishes in the family
Callichthyidae, which includes the genera Aspidoras, Brochis and Corydoras. These fish are able to consume atmospheric oxygen, which is absorbed into the bloodstream through their modified vascularized intestine. This enables these fish to live in oxygen-starved water in their natural habitat. It is not uncommon for the aquarist to observe these fish making a rapid ascent to the surface and calmly settle back on the bottom. Consequently, a cover is advised, as I have more than once found an individual on the floor after such an event. These catfishes are diurnal and are interesting to watch as they swim across the gravel with their snouts going over the gravel for uneaten food. In addition, these catfishes will not uproot live plants.
Callichthyids commonly available include the leopard catfish (Corydoras trilineatus), peppered cory (C. paleatus), green brochis (Brochis splendens), bronze cory (C. aeneus), masked cory (C. metae) and panda cory (C. panda). All of these species range from 2 to 2.5 inches in length.
Callichthyids are tolerant of a wide range of water conditions, but extreme pH and hardness should be avoided. Slightly acidic to neutral (pH 6.5 to 7.5) water with a temperature between 72 and 79 degrees will suffice for most species. In addition to their scavenging activities, supplement their diet with a variety of prepared sinking foods and live worms. These fish should be kept in groups. Due to their docile nature and small size, more than one can easily be kept in a small community aquarium, while small schools can be kept in larger aquaria.