The algae will be gone within a few days then, and then you will have to supplement food for them, which has to be accessible almost all the time. And that's when a 10 gallon can be trouble, as the food is a negative factor for water quality. And Otos are quite sensitive to
nitrates so get ready for more and bigger waterchanges.
3 is already not enough Otos in a group. I wouldn't do it, but I can't stop you and maybe you should experience it yourself.
And when all this is somehow worked through and solutions found: Many Otos are wild caught and tend to have really persistent parasites. I lost my last Oto months ago and the parasites still kill fish in my tank. So try at least to get tank bred Otos.