What can you benefit from a Janitor fish when once it was known as useless fish?

Answer 1

There's no such thing as a Janitor Fish. That term was invented by pet stores and pretty much tagged to any bottom dweller or suckermouth fish - of which there are hundreds of species of fish. None of these fish will clean the tank for you, which is why the term "janitor" is completely inaccurate!

To be honest, if you see any store selling a fish under the name "janitor fish", walk out and find a better aquatic store that actually know what they're selling!

Commonly sold "janitors" include Common Plecos (of which there are hundreds of species even called that) which get over a foot long and are horrendously messy animals, entirely the opposite of any kind of cleaner. Also Chinese Algae Eaters may be sold as "janitors" - they get about 10" long and turn predatory as they mature!

There are however a number of different types of dwarf pleco, which stay small, and are good algae eaters. An example would be the bushynose plecos. There are also other catfish, such as otto cats, which also eat algae and stay very small (less than 2 inches long).

There are also many types of scavenger fish, which help to eat leftover or excess food items. The scavengers you will find in pet shops are usually either Cory Catfish, or loaches, most of which stay reasonably small.