I have purchased this rock as well and I DO NOT recommend it. I had several weird things happen with my tank - mysterious fish death, brown slime covering all rocks, and lack of Coraline algae - and when I removed this rock from my tank, it all went away after a month.
After looking at this rock when it had been dried, it appears that this company applies paint to the surface of the rock to mimic the look of coraline algae. It honestly looks like the "splatter paint" stuff you see kids playing with. In addition, it's all synthetic rock, which looks like some form of concrete poured into a mold. I cant imagine anything good comes from concrete, and especially the paint. If you're getting weird reading from the tank, I'd guess it was the rock.
I bought this stuff when I was brand new to the hobby, thinking it was great rock, but after seeing other rock, I realized it's a ripoff! The amount of life you get on other forms of live rock is many times greater than that for this rock. It's just not worth it. I'm all for lessening our environmental impact on coral reefs - but sometimes you just need the real thing. This is not a place where I think the "synthetic" live rock is a valid replacement for real live rock.
