after 7 years.... you should test No3 and Po3, without a doubt they are higher than they should be. The higher nutrients is why you have excess algae (fuzzy) . I have never removed my rocks to clean them (almost at 7yrs now too), but I do - on a rotating basis, clean/siphon the DSB. every 4-5 months I clean 1/4 section. This helps get the gunk and deep settling debree out. I have a sulfur denitrator for No3, and run GFO + drip lanthanum chloride for PO4.