I've had two of these catfish for nearly a year. They're in a 60 L tank with two blue rams. They all get on great. All my fish never hide or get scared when I clean the gravel. They are all over at the cleaner picking at bits of food. They are so hardy. They say cory cats are great at cleaning the leftover food up of the bottom of the tank, but my two cats are great, eat everything. It's great watching the two otos and the two rams all joshiling for the food and never had any problems at all. I feed all kinds of food, live to flake
The only way an Oto catfish will attack another fish is if he is hungry. It is a misconception that you can just let them live off the algae, they will eat it all and starve.
These are an indispensable asset for any planted aquarium. I have a 280 liter, fully planted with african ferns, crypts, subulata (grass), tenellus (smaller grass) etc. When I just had 2 Oto's, I usually had a dark, slimy algae growing on some plants...usually older ones such as strands of subulata, which reached the top of the tank. I put in 6 more, now there isn't any algae anywhere. No exaggeration, they clean up and down individual strands of tenellus and subulata, and take care of the slower growing ferns for me. Even that crusty gray stuff that gets on anubias is no match. After about 2 weeks it has begun to crack and flake off. The back glass is shiny again. These guys are essential in my opinion. When you have flake food settling on african ferns near the surface, they tend to rot and make a black spot on the normally beautiful light green leaves. These little guys (or gals) will scrape every cm of every plant and get this extra food off. My tanks look better than ever, with every leaf free from algae. I cannot accurately describe the difference. Make sure to feed them. Remember, if they can rid a 280 liter tank of all visible algae in a matter of days, when it's gone, they'll be hungry. Oh, they are cool fish too!
If you think your Suckermouth catfish are not getting enough food, I have found that if you place a piece of cucumber on the bottom of you tank (you will need to place it under a rock or secure it to the bottom as it floats) the Suckermouth catfish will start to eat that!
I have kept Otos for about a year now. They are the best algae eater for a planted tank. They do not hurt the plants at all. They do a great job eating all the algae and even get in the small spaces in the middle of very bushy plants. They definately need company. I had one in my 20 liter and he was always skittish. I moved one of the five from my 200 liter to the 20 liter to keep the lonely one company. He is not nearly as shy any more. But now I think he is a she and the new one is a he since she is very fat and he is following her around alot. I found her on the floor yesterday. I am thinking that maybe her boyfriend got a little too excited and scared her. She was a little dry and fuzzy, but is looking better today. I covered the top of the tank completely so it won't happen again. I've noticed that sometimes they will be resting on a plant or piece of decoration with their nose pointed up and you would assume that they are sucking with their mouth to hold on like a pleco would. But when I look closely, they are actually gripping on to it with their pelvic fins!
Otos have gained a reputation for dying off for unknown reasons after introduction to a new tank. My experience is that otos are a very hardy fish. Just introduce them slowly and they should be fine in just about any condition. I have had otos that have thrived in both pH 6.0 softwater tanks and pH 8.2 hardwater african Tanganyika cichlid tanks!