I know the fhm used it. I regularly saw schools of fry around them. Though I believe a lot of times it was cnbg fry. Algae did grow on them some and you could see tiny fish feeding off that. Also I regularly could catch at least small lmb around them. I know a few times lmb spawned next to them. Also my pond is so low I can see a complete empty colony of cnbg beds out in front of them. So in my opinion it was one of the best things I did for my pond! Now I just need rain!!