How long have you had the tank? A pleco usually takes care of that. Are you over feeding at all? Sometimes it can be due to over feeding. Also what are your NitrAtes? High Nitrates can cause algae. For now, you may just have to scrub it yourself if the algae eaters are not doing a good job. I still get a bit of algae here and there but I usually clean my tanks once a week and scrub it myself because my plecos are getting pretty lazy, LOL. Leaving your lights off longer will help a bit. Is your tank near a window?
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