Blackout just denies the algae the light they need to survive. Generally speaking, the plants and fish can survive a few days without light, but the algae die off. Just cover your tank up with something that doesn't allow light to penetrate (black plastic, blanket, sleeping bag), feed the fish sneakily (without allowing lots of light for extended periods) and your algae should disappear.
I feel I must also add that I've found that the green algae is not something I've found anything ever eats (snails, plecos or any other fish). I made the mistake of leaving my light on one week on holiday and spent ages scrubbing the green monster off of everything in the tank except for the fish. Should have bit the bullet and wrapped the tank up, but I didn't discover this site in time. Other algae gets eaten, but not the green.