algae

[asylumdown]

The fact that your tank is still cycling means you shouldn't do anything other than maybe cut your lights. Algae is a normal part of the process. Sterilizing your rock with acid will just take you right back to where you started, and should be used as a last resort for truly insidious species of algae that show up in stable systems and can't be removed any other way. You'll see many different kinds of algae pop up, spread, then recede as your tank matures.

Edit: I just looked at the pic, it looks like you have a mix of true live-rock mixed with marco rock, and that the algae is on the live-rock. This is completely normal, and the algae will very likely spread to the marco rock soon. Again, completely normal process of the tank cycling and becoming populated with an ecology. Dipping your live-rock in acid - which I assume you bought specifically to seed your marco rock - would be extremely counter-productive at this stage.