Excel is very effective on BBA especially if spot treated. I've not found it to be effective on staghorn or hair algae.
If it is staghorn, the best way is to spend a few days working on different sections of the tank and get it all out. A blackout will do nothing to help you.
If it is staghorn, the best way is to spend a few days working on different sections of the tank and get it all out. A blackout will do nothing to help you.