Honeycomb Base Rock


I had this posted in the New Hobbiest forum and it was suggested that I post it here and ask you for more information on the rock... what it's made of, why you're not selling it anymore, etc. Any help would be very much appreciated. Thanks!
I've had my tank set up for going on 2 years now. I was trying to cut corners & save money, so I originally purchased some Honeycomb Base Rock from this site (I've since noticed that they no longer carry it). I like the shapes of the rocks, but they seem to really hold on to nusaince algaes. I have 50lbs of BR and 2 other rocks that were originally "live rocks". The LR has little to no algae on it and the base rocks are covered in something that looks similar to cyano. It's not slimy though... it looks more fuzzy. And I can't get it to scrub off of the rock... it looks almost stained. Anyway, I finally broke down and ordered 50lbs of live rock. It's in the process of curing right now. I'd love to keep most of my old base rock and just add the new stuff in addition to it, but I'm wondering if it would be a better idea to take out the base rock and let it dry out... maybe scrub all of the crap off of it and possibly add it back in later. I just find it really weird that those rocks are covered in the algae and the LR has almost none on it, even though it's stacked right in with the other stuff. Any opinions or suggestions?
It's a 55gal currently FO with 2x54w T5 (soon to be 4x54w when I transition to corals) with individual reflectors.