Well the reason of algea can be cause your tank still needs to mature... and well another agents are HIGH PHOSPHATES & NITRATES... so you should cut back on feeding a good thing will be feed your fish everyother day, and also if you can any phosphate remover media.
i used to have high nitrates but know not ... cause i do big water changes and i run some filter medias to purify the water more... i use SEAGEL (carbon & phosphate remover), PURIGEN (removes nitrates) & Polyfilter (removes any harmful metals)...
ED