Originally Posted by
Bacon
My guess is that any smooth surface that grows algae is actually growing algae on top of a calcification layer. Think about it. scrub your glass with a magfloat and any spots of coralline that don't come off, that's where the algae grows first and fastest. Scrape it all off with a razor and it takes a while to come back. Same with power head in your tank, they get a coating of coralline, and you can take them out and scrub but unless you soak in vinegar, that algae will come back fast.