Aquarium hobbyists are usually fairly fastidious about their aquariums, and while they are willing to help maintain the aquarium with the best filtration and water changes, they are always on the lookout for help from the fish. The aquarium will usually have some type of mix of fish known to be part of the “clean-up crew.” Beginning hobbyists will usually ask for fish that will eat the wastes of the other fish. I am sorry to say that such a fish does not really exist. Many scavengers will “shift” through the wastes looking for bits of edible pieces and while doing so will break up the wastes and cause them to crumble into the rocks and substrate, but the majority of the wastes are still there. In freshwater applications, the Corydoras catfish and Loaches make up some of the best scavengers for this task. They constantly search the bottom for food and have the right mouth structure to reach into small cracks and crevasses. Many Cichlids and even Goldfish will also constantly pick up the substrate and chew on it looking for bits of food. We can usually depend on these types of fish to help maintain the appearance of the aquarium. But the wastes are still there. Fortunately, heterotrophic bacteria will start to digest a large percentage of the wastes until all that is left is inedible compounds, a process called mineralization.
Perhaps the fish with the hardest job are those hobbyists use to control the algae. It is important to stress that these fish help control algae, but they will never completely eliminate it. The best known of these fish is the Plecostomus, a generic name given to a large class of sucker-mouth catfish. Most Plecos have heavy armored scales along their backs and under-slung mouths that act like suction cups to attach them to smooth surfaces. The Plecostomus has many rows of short teeth that it uses to rasp the algae from the surface. While they do a pretty good job with algae control, there are some drawbacks to Plecostomus. Some of the species can get very large, and as they grow, they are less likely to eat as much of the algae and learn to adapt to eating the commercial fish foods we are feeding to the other fish. (I have had Plecostomus that learned to swim along the surface upside down to be able to grasp floating pellets from the surface!) Their large sizes also can start to knock over ornaments and break any live plants when they attempt to eat algae from the leaves of the plant. There are some types of Plecostomus that will remain smaller, including the Clown Plecostomus, the Rubber Plecostomus, and the Bushy Nose Plecostomus (sometimes called a Medusa Plecostomus because of the unusual protuberances that grow along the head). The Otocinclus is another smaller algae eating fish that is a favorite for algae control in a planted aquarium. The Chinese Algae Eater is actually a poor choice for algae control and can annoy the other fish in the aquarium. In a small fish community aquarium, you could also use Mystery Snails to control algae. Also, in a small fish community aquarium you could use Algae Eating Shrimp to help control types of hair algae. You just have to make sure none of the fish will consider the shrimp part of the dinner offerings!
Clean-up crews are a great addition to any aquarium and will help promote better water quality for all of the fish/plants in the aquarium. While they can slow down the frequency needed for cleaning, you cannot expect to eliminate cleanings with the use of clean-up crews – that is just putting too much faith in their work and capabilities.