The sids are not aggressive whatsoever! My otos do the loachy dance with the sids up and down the glass. The first six I bought I kept in my discus tank for several months and they didn't bother any of those fish in there either. Their barbels look more like whiskers than barbels that say cories have, and I think they are a bit stiffer as well. So sometimes when the sids nudge up to a pleco or a cory, the result seems to show that the feel of that is a bit prickly. And as I've said before, the cories spawn all the time and the sids go absolutely crazy for the eggs. Last time I spotted one of the sids trying to snitch the cory eggs out from in between her fins before she had placed them down! So impatient! The sids are funny. In some ways they remind me of tiny porpoises!