Problem with Green Spot Algae in Planted Tank

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Hi, my aquarium grows green spot algae very quickly all over the glass and even on to fast growing plants such as water sprite. My aquarium is a 2 ft, ~40cm deep tank lighted with 2 x T5 super sun lights. I do CO2 fertilization, 1 bubble in 2 seconds. I've tried adding Seachem Flourish Phosphates, and nerite snails, but the GSA keep on growing. Please help!