brown algae

[clair]

Just wondering if anyone can help out here. I've rescently set-up a 60g tank(2 weeks) A grey lava rock approx 10-15lbs is used as base & 20lbs of live rock. I'm getting this brown algae growing what seems like by the minute all over the sand bed & LR. I've got a canister filter with carbon, a maxijet 900 for water flow. Is it possible that the algae is coming from the lava rock's chemical make-up? It's got alot of differnt shiny blues & greens in it(lava rock)