Black Brotula cleaning Green Moray
Black widows are part time cleaners as well...
I've talked to LCK 110 staff and was told they have never brought in either black widows or lightning wrasse before, i wonder if you have gotten your info wrong?
All species of brotula which are the group of fish black widows come from have been reported to be reef safe. And the brotula is a type of goby, so far have not heard of any of these species eating coral. so your account is very unusual...
As for lightning wrasse I have seen overseas hobbyists keeping them in reeftanks with no problems whatsoever.
And isn't it funny for a fish found in a coral reef to be non-reef safe??
I have yet to hear of mass devastated patches of coral by fishes except for parrot fishes...
If your fish nibble corals it would most likely due to the fact that your fish are unwell or not well fed?