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They ignore them until they have eggs or fry to protect, at which time a guarding mother might attack the eyes if the Otocinclus (or Corydoras, Farlowella, etc) blunders too close. I have not had Apistos pluck out catfish eyes (yet) but Nannacara mothers sure will.
I've had the same experience as slimbolen- even when guarding eggs or fry, Apistos don't even seem to regard otos as fish. They're just little algae robots or something. Corys, on the other hand, will get chased away ruthlessly.