Wow that LFS is evil. They are just trying to rip you off with over priced band-aids-just like that good for nothing tetra Algae killer. Green water is not a big deal. You have lots of little plants floating around in your water. Just be thankful they haven't latched on to all your plants killing all the leaves. Green water will not develop without nutrients. Either your root tabs are leaching nutrients into the water column, or you are adding tons of fish food or there is a dead fish rotting in there.. The second thing they really need is light. Your light sounds great for these tanks, but the thing is photoperiod. Forgetting to turn your lights off for a day or 2 will cause green water in no time(AS LONG AS THERE ARE NUTRIENTS PRESENT (Algae is not a paranormal being, it needs the basic building blocks to multiply as do most all living things: C, N, P)).