Distribution: America South; Brazil, South America
Main Ecosystem: River; River
Temperament: Peaceful; Peaceful. Do not combine with agressive fish.
Diet: Herbivore; Herbivore
Care: Feed sinking algae wafers, zucchini. Do not scrape the algae from the back glass as this will be eaten. Regular water changes and good filtration are required. Broad leaved plants are essential. They can be very delicate fish though, if proper care is not given them. They fare best with very clean water and live plants. When adding these fish to your tank, acclimate them for much longer than usual to avoid problems.
pH: 6.0 - 8.0
Temperature: 20C - 26C (68F - 79F)
Hardness: 5 - 19 dH
Potential Size: Male: 5cm (2")
Female: 5cm (2")
Water Region: Bottom; Bottom
Activity: Nocturnal; Nocturnal
Gender: Difficult to determine. Females grow larger and are rounder bodied.
Breeding: Can be difficult. Lower the water level and raise the temperature slightly. Then add water to the tank through a watering can, at the original temperature. The eggs will be laid under leaves.
Did you know that the oto is a fish with its own website? While I do not like to refer people to other places unnecessarily this site is one I use all the time as this gentleman had devoted his life to the study of the little fish. It is appropriately at:
I have written the gentleman myself and he is wonderful to talk to.
Otos have very rarely been known to breed in captivity and this is the reason that they are so harshly treated in this world. Catching them to sell these popular little fish is horrific and mean to them. Flooding the streams with cyanide gas to slow them down to catch them kills half of the catch and the transport of fish who are weakened further causes deaths. Then they hit the stores where they are given in a lot of cases the same flake foods that the other fish are getting and their bodies are just not equipped to deal with this type of nutrition so many of them die in the Fish Stores waiting for a home.
For those who have not heard it before there are 3 main things to look for in a good candidate for a healthy oto:
Rounded bellies but not bloated
White abdomen area with no red streaks (occasional light pink is present and is a caution but generally not fatal)
Eyes should look like they are not clouded over.
Thin fish or sunken bellies can mean that the fish has starved and once they reach this stage they have lost the ability to digest food (the bacteria in their stomachs that does the digesting has died) and they can eat a bushel of algae but will die of starvation due to the inability to use the food.
Reddened abdomens are a sign of infection and once it has reached this stage with these being fairly fragile fish during the initial ownership period, they generally do not survive.
I will say that if you get them past the first 30 days of quarantine (they really need a 30 day quarantine) they can be and like mine will sometimes be some of the most long lived fish you own. All of the otos I have at present are older than any of my other fish at present. They are healthy and their only requirement that I consider to be absolute is live plants in the tank. They get fed algae wafers a couple times a week and other than that they do very well on their own. You should never keep more than 2 otos per 5 gallons of tank size and less than that if you have any other algae eating fish. They will not have enough to keep them going if you do. While they will eat algae wafers they do need some naturally occuring algae in the tank even if it is only the type that is not visible to the naked eye.
I am sorry that I wrote a book but this is one fish that I love and I can get on a soap box very easily over them. Sexing them is not easy I do not think I would even try as they do not breed in captivity usually. You could see if you could get ahold of the gentleman on the otocinclus site to see if there is a simple way but I do not think there is one really. None of my books has a way of telling listed.
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