Great!!! Ok he used live sand... If it was play sand from hardware store my next guess would have been to much silica in the water that the algae was feeding on. If there is big chunks that you can just pull off peel it.
Yep! I can tell you that he didn't really cut any major corners with the setup in terms of quality of materials, and it is a basic reef setup with just the lighting, skimmer and a sump w/ filter sock. The only thing the tank could use more of right away is live rock. Speaking of which, what's the best way to clean the rock off? Just pull it out into old tank water, scrub it with a brush and then go back in?
. Over the weekend I made some changes to the tank, including the installation of the additional powerhead. I adjusted the return tubes to aim at the top to keep the surface water moving, and now have 2 powerheads (850 gph) aimed basically at each other on opposite ends. Tell me what you think!

