Regular weekly water changes-I do 50% a week, it depends on your stocking. If there are light stocked fish you could maybe get away with 20 or 30% a week and scheduled light should help, so should adding more live plants if you can. The algae on the glass can be easily removed with a scouring pad (never used for anything but the fish tank.) Your snail should help clean up the decor a little but the other three things will help a bit faster