It is true that nipping helps growth...I don't have alot of SPS yet. As I was overfeeding to make sure that the copperband would make it. So far, no issues of nipping with the LPS and some SPS. There is a school of thought that thinks that some nipping by angels are good for SPS dominate tanks as it promotes new growth. My LFS told me that, he may just wanted to sell me the Potter's Angel. Do your own research.
in a 500 gallon established system where the nipping can be distributed
