Green Algae

[pam_redbeach]

I took over a 40 from the people who sold me their house and have had great success and pleasure since the acquisition in Nov 2001. That is, until recently, when slimy green algae started growing on my LR and LS. I have tried decreasing light duration, but it's not helping. Also, I have had some snail casualties. All corals and fish are fine, skimmer needs cleaning a lot more now. I clean algae off LR and LS once a week, but it grows back voraciously. Pet store suggested adding glenny to tank, but I would rather not. Please help.