I'd never seen one of these Zebra Oto's in person before, so I'm quite impressed with the size of them. They seem about full grown & much more mature than the O. vittatus I picked up from PetSmart back in July. My O. vittatus are about 1/3 the size of the Zebras. The Zebras also seem to be brave & out in the open all of the time. My O. vittatus seem scared & just hide underneath a crypt in the shade & flip out with any movement close to the tank like just walking by. I'm starting to favor the Zebras over the vittatus in every category at this point & I've only had them for a couple hours now!