RD -

I have some low-flow area (some things are beginning to outgrow my tank), and there's been a patch of cyanobacteria slowly growing over the past month. My diadema urchin didn't touch it. It is still a very good animal to have, as Matt says. It just didn't work on cyano for me. Haven't tried any conchs, but I'd like to.

Anyway, just remember you need to feed the urchin if there's not enough for him to find in your tank. I like them because it's more diversity, and as Matt points out they are selective herbivores, rather than vultures.

On cyanobacteria specifically, I have to say I don't know how to beat it. It rears its head once every few years, and I end up having to vacuum it up.

Let us know if you learn anything.

Dean