Otos can be finicky about food. I did my homework ahead of time, and from what I read, if they're not touching the algae already in the tank, they probably won't take anything else you offer, which means they won't add much to the bioload for as long as they survive. My problem with them was never getting them to eat the algae, it's getting them to eat anything else when they're done.
Didn't really think of shrimp, but they're definitely negligible bioload - Shrimper made a post the other day that you can count 8 ghost shrimp similar as 1 inch of fish for the inch-per-gallon rule, and he seems to be a shrimp authority in the invertebrate forum. An apple snail might help, too - you can have one and not worry about snails overrunning your tank.
Bioload is equal to food intake, though (what goes in one end comes out the other), so enough shrimp to equal the algae eating capacity of otos will also equal the bioload.