Well adding algae to the tank certainly didn't help now did it? j/k :tong:
Inspecting Live Rock before you add it to your tank is a great habit to get into, especially if you pick up the rock from a fellow aquarist. All kinds of pests and nuisances can enter via your rock. At least the algae is visible, and scrubbing it off with a toothbrush before you add it to the tank is a step in the right direction.
After that, as Tim stated, good maintenance habits come into play. Manual removal (depending on the severity of the outbreak), going easy on your feeding, watching for low flow or dead zones where deritus and excess food can pile up, etc... A clean up crew will aid in the removal of some of the deritus and excess food, but hoping that they will make a noticeable impact in algae reduction is a long shot. You may get lucky and some hermits or snails will pick at it, but they won't eradicate it. Also, the brown algae you are seeing is more than likely diatoms, and should recede on it's own in time.
Yasha Hase White Ray Gobies are ALWAYS my recommendation for any tank.
Good luck.