I think what you've got is fine, but it would be considered a low-light tank. 2 x 40 = 80W. 80/50=1.6W/gal. Usually 2-3 would be medium light. Also, shop lights usually just have white paint on them for reflectors, which work great, but not as well as those shiny polished metal ones that a lot of aquarium lights have. Wouldn't hurt to get more light, and your algae issues are probably related.