Most all oto's are wild caught and many are caught by the use of cyanide added to the water to stun them and make catching easier. They also eat a lot of biofilm when kept in an aquarium and a good biofilm layer takes time to build up. Some oto's will eat fresh veggies like zucchini or processed food such as algae wafers but many don't so a tank needs to have enough natural algae (diatoms and green dust algae) and biofilm to support them. Also a mature tank has stable water parameters which are best for oto's. So taking all this info into consideration is why I don't suggest adding oto's to a new tank set up. I'm not saying it can't be done but it's best IMO to wait on adding them.