In all honesty, I've never worried about it. I'm sure they're getting a good enough share even if you aren't noticing them eating the pellets. Keep in mind otos are very small and can be sustained by very small amounts of naturally occurring algae, and most bottom feeders will find all sorts of food to munch on that the other fish left behind, so I wouldn't worry too much unless you noticed a definite issue with one or more of the fish looking emaciated (sp?).