"pre-opened" my pool last month. that is I got the pump going, did an initial scrub and vacuum and added chlorine. Haven't done much since. With cool weather water stayed clear. today I vacuumed very good and removed all leaves and debris. Water wad clear and no signs of algae. I then added about six pounds of Sodium Dichloro-S-Triazinetrione and in about ten minute the entire pool was pea green. It is supposed to go the other way. Put chlorine in green water and it turns clear. Why did this happen? Not sure what to do. I have always used calcium hypochlorite before. Does Sodium Dichloro-S-Triazinetrione act differently?