Mine I've done like 6 times now. Last time I tweezed off what I could then did a peroxide dip using 3% hydrogen peroxide and tank water. I did a strong mix probably 60/40 water to peroxide and left it in there for 15 minutes. So far no more algae growing out of that piece.Okay. Actually going to GSD now. In the meanwhile, if anyone has any hot tips for getting the algae off my pipe organ, I'm all ears. It's being strangled to death.