I was going to say otocinclus, but then realised that they're basically plecos. They're very nice, though. Maybe shrimp? Not looked into the water hardness preferences for a lot of shrimp but it might be an option.
Yes, otos are a great fish. Those, cory and kuhli loach are the only bottom feeders or cats I keep. I suppose I now have to include a Chinese algae eater I acquired along with some glo danio and housed in my plant grow out tank.
Otos have been my go to for a long time now, I currently have 18 tanks of various sizes and they are in all but about 3 or 4. Great little workers and I have no issue getting more for my apisto tank project, but I'm getting a little nerdy and deep diving into alternatives.
You know how it goes, you make a list of possible fish, then research and find out that one gets to 2 feet long... Then you rethink.