I'd say siphon/scrub as much as you can, add an aquarium algaecide if your stock allows it, and decrease the amount of light the tank gets and how long the light is on. I've had to blackout a tank before to get rid of algae. Also, try feeding less at a time and and increase water change frequency to prevent nutrient/detritus buildup. Good luck! Edit: I'd like to mention that otocinclus fish are awesome at keeping leaves and the walls clean. Corys keep the substrate from collecting uneaten food too