Black stuff growing on rocks

[claymax]

ok, i have a bit of a cyano breakout, black to purple black in colour, i am only running aqua clears, and 2 fans (waiting on some money for a canister). ive derived that i left the lights on too much and my newly added rock leached some phosphates, and then bam, black covered everything. all i have is the LR and some sand in there, and ive been cycling for a few weeks now. so what tips can i get to get rid of it besides turn out the lights, change the water and scrape it out of there. also note STRICT BUDGET. for now