Okay, 12-8. That's kind of a short light time. And what about your light? You didn't answer where they were at. Whites and Reds & Greens. You wont over do Microbacter if you follow the instructions on the bottle. I dose Microbacter Clean @ 5ml daily when I have algae problems for 2 weeks straight. And just because you have already went through the ugly stage doesn't mean that it can't come back. Clearly this is what you are seeing right now is that it has come back. I really would do an ICP test if I were you. And change your lighting.12 in the afternoon 8 at nite tank is about 7 months old already went through dino bloom and red slime for nitrates I have a marine pure 8x8 block was gonna add more but didn’t want to over do it I do have microbacter 7 on hand