In regards to the urchin, I am quite sure it is a Diadema.
Here's a picture...
His 'butt' has the orange ring around the 'bubble' and has blue dots versus lines.
He a suspect in some of my xenia loss and zoo loss. I have had sick stalks dissapear, as well as tranplanted zoo loss. He hasn't touched anything other corals that I suspect him of. Other corals in my tank include mushrooms, anthelias, hammer, bubble, and brain. My urchin is defiantley a coraline muncher. He leaves he classic white trail of newly exposed rock. He is always crapping out small grains of sand, which I suspect is pulled off with the coraline. When I first introduced him, I had some hair algae, which I am sure he has consumed.
In regards to the Dictyota, I have had it since the start of my tank. I have taken as much rock out as I could, and toothbrushed and rinsed. It has always grown back to the point where it is a carpet of moss. In reality it isn't so bad, but it has spread, and I don't want a moss tank.
Nothing in my tank touches it. Alage eaters include:
Astrea, blue hermits (now in the sump... snail killers), nass snails, bumble bee snails, sailfin tang, lawnmower (RIP), and the Diadema.
I believe I could turn my sump into a refugium. But honestly I didn't want to go through the trouble. Currently guessing I have a 20g plexi sump, baffles on both sides, with about a 10g section in the middle that has an inch of CC. All I'd need do is add the plants and the lights.
I believe my water conditions are good, no nitrates or phosphates detected. The only advantage would be increased pod production, which is never bad.
