If you want it done fast (and it's just GHA): scrub rocks with soft vegetable brush and rinse in salt water tub (don't leave the rock out of the water while you are cleaning other pieces). I would place a good powerhead in the SW rinse tub as well to blow off/out detritus. You should get most of the GHA off so it can go back in the tank. If you want, you can do a 3-7 day blackout after this but again if its just GHA and you are using RO/DI and have a good CUC, I see no reason to do that.
Long route: 3-7 day blackout (either in the tank or in a separate tub). Fish and LR will be fine w/out light but if you have corals I wouldn't go past 3 days. The algae should just die off or can be blown off and siphoned fairly easily. If you do it in tank, I would do a good WC at the end.
HTH
Long route: 3-7 day blackout (either in the tank or in a separate tub). Fish and LR will be fine w/out light but if you have corals I wouldn't go past 3 days. The algae should just die off or can be blown off and siphoned fairly easily. If you do it in tank, I would do a good WC at the end.
HTH