This is an interesting conversation. Just to add to the anecdotal evidence I’ve got a mixed reef 32 gallon with a number of Acro frags doing very well. And a foot long nepthea which was one of my first corals. The 2 acros nearest are by far the slowest growers. I do run carbon but figure there’s a chance it’s the leather that is the reason for it. Can’t be sure but it might be. The leather is by itself. It can come close to touching my frogspawn sometimes. But those 2 don’t seem to bother each other.