They don't need to be in a group at all Scuppers. They are not a schooling fish. One alone will do just fine. What size tank do you have?
PM'd everyone. And thanks!!!![]()
What's in the 75G? That would be my initial suggestion. Killies can be pecky towards the fins and GBR's are so territorial when they are breeding. I usually advise people to keep them in a minimum of 29g/30G. So let me know what else is in the 75G. While you probably won't see it for days on end (I have a young one in a 72G alone), it will grow nicely in there.
You're tank is really very, very nice! Looks like you keep it immaculately clean too. Lots of activity. There is nothing in that tank that would compete with the pleco for soft algae and biofilm and you've got plenty of driftwood for the pleco to hang out on. I don't think the angels would create any problems for the pleco.