Many of the fish that help clean aquariums grow to be quite large, which can be problematic. That is why many people who have home aquariums prefer to use a smaller fish, such as the cory catfish or corydoras, which usually only grow to be between 1 inch and 4.7 inches long. The most popular cory catfish are the Bronze Cory, Peppered Cory and Panda Cory.
These fish can not be kept in just any aquarium, however. You need to take care to provide the right water conditions and give these fish the proper type of food and living conditions. If you do this, your cory catfish may even live to be 15 or 20 years old, helping you to keep your water and aquarium clean. They can't do all of the work though; you will still need to do your part and change the water from time to time.
Cory catfish typically swim in large schools, which means you can't expect them to be happy if you just get one for your aquarium. You need to get at least three and preferably six or more for the best results. Don't worry, these fish can be entertaining and will not spend all of their time skulking about on the bottom of the aquarium. They get along well with most other community fish since they are relatively peaceful.
When it comes to water conditions, tropical temperatures are best, although they can tolerate some variation in water temperature. More importantly, you need to limit the amount of salt and nitrates in the water, and keep the pH neutral. The water should be soft to moderately hard.
Corydoras also need you to give them foods similar to that which they would get in the wild. They will eat some of the fish flakes that eventually float down to the bottom of the tank, but they will do better if you also give them capsules of food that sink to the bottom or live food as well.
Treat these fish well and they will help break down any debris in the aquarium before it causes the ammonia levels to rise too much. Try to avoid having sharp substrate in the aquarium, however, as this can injure the fish. They do enjoy having plants around, so you should include some of these.