I used fenben infused fish flakes every few days for a month and it didn’t kill anything other than a Green Star Polyp colony which retracted shortly after the very first dose and never recovered even after being moved to a separate tank within 24 hours. I wasn’t trying to kill BSP (I don’t have any), I was dosing to make sure the vermitid snail population would be further crippled. I had no noticeable change in parameters. I had a cleaner shrimp which passed around around that time—that may or may not be related,but my 4 conch, 2 urchins, and army of snails were unaffected. The dosing is very small: one small pinch of flakes per 100g per guidances from Chris Meckley who uses these flakes on his farm system once a week to control SPS pests and vermitids, I stopped dosing since I did a tank reset where I replaced my entire rockscape. There are a few vermitids in my pipes and overflow box (much less than one year ago) but they don’t seem to bother anything.