Thing with plecos is that they get lazy. Its rare for them to actually "kill" another fish but it does happen. When I was more into fw I had a royal pleco that was a lazy good for nothing till he got a taste for discus and started to literally jumping on the sides of them and sucking on them till they stressed out so much it killed them. The Otto cats are great additions and won't harm anything. i would keep those barbs fed well. Ive heard some stories here and there that they can and have turn to eating other fish if tempted enough. And you can never have to much filtration for a fw! When I did tropheus I had a wetdry rated for a 120 and 2 2215 classics. Clean tank = super happy trophs. Edit: that's whst I grt for not reading thoroughly. Thoguht you had albino bristle nose plecos but yet Chinese algae eaters woth do the same thing as some plecos will.