After looking through the forum, I've seen some threads about users on here having their Otocinclus Catfish die. This thread is to give information about how to keep the Otocinclus happy and healthy and to provide information to those who want to purchase one. About the Otocinclus Catfish The Otocinclus Catfish, also know as the Oto or Dwarf Sucker, is one of the smallest in the Loricariidae Family. The adult size of the Oto is about 1.5 inches. It originates from South America in the lower Amazon basin. The Oto is a great algae eater that will eat away brown algae off glass, decor, plants, and any other algae based objects. It can be sensitive to water parameters so a Ph of 5.5ppm to 7.5ppm, Ammonia and Nitrites of 0ppm, and Nitrates of 0-20ppm is ideal. Looking at these parameters, the Oto is not a hardy fish and should be put in a well established cycled tank. They DO require a well established tank and stable parameters to thrive. They are also very sensitive to medications. If certain medications are added or have been added to the tank you plan on putting otos in they will most likely die. Before buying Otos, make sure your tank has brown algae in it. Otos do not do well in shipping and may become very stressed that they will not eat for a couple days after putting them in your tank. If there is algae in there for them to eat after becoming unstressed, they will happily eat the algae and will most likely survive. The otos may look very inactive during the day but that is because they are most active at night. They are a great substitute for the Plecostomus. They produce little waste and don't grow as big as the plecostomus. Tank Setup The Oto will be fine in a tank that is 5 U.S. gallons or larger. They like the water temperature to be 70-78 degrees Fahrenheit. The Oto likes a planted tank with some algae in it for it to eat. They are very peaceful and are compatible with other small peaceful fish. Any substrate is fine for the Oto. Driftwood or caves will provide hiding places for the oto to help it from becoming stressed. Otos like to have a few friends with them so purchasing 1-3 otos for smaller tanks is fine. For larger tanks, it's best if kept in groups of 6 or more. Your tank should have good filtration for the Otos. If you have a tank setup similar to this, Otos will thrive in your tank and be healthy and happy. Feeding A tank with brown algae will keep the Oto fed. If brown algae is not present, feed them algae wafers, cucumbers, lettuce, and zucchini. Breeding And Sexing Sexing the Otocinclus is very simple. The females are larger then the slender males. The ease of breeding the Oto is moderate to very difficult. There are currently 13 species of Otocinclus. I have not bred Otos but I have some information that could possibly help if you are interested. Breeding report on Otocinclus vestitus By reading this article you should have an understanding on how to successfully keep Otocinclus Catfish alive in your tank. I currently have 2 otos in my 10g right now and they do a great job of cleaning all the algae off the walls. They are a great fish to have and can do wonders to a tank full of algae.