Probably around 200lbs worth...most of my rock does not have a problem but some of it does. Some of it has green slime algae growing on it and one of them has a bit of dense hair algae. Also have green slime algae growing in certain spots on the sandbed. My nitrates used to be 50 but was able to bring that down to around 10-15 by getting rid of my refugium and a few massive water changes. I used to have sand, rock and some chaeto in the refugium and all that did was grow cyano in there and accumulate detritus. Once i cleaned that out completely, 75% of my issues went away including cyano in display but now i just have a bit of this green slime algae left.