another alge question,

hmmm if your tank is a year old it should be fairly matured, unless you are going through a mini-cycle for some reason. What and how much are you feeding? Have you had other algae problems recently? What kind of corals are you keeping? a 12 hour halide cycle does sound a little long to me, cutting it down a little couldnt hurt. Algae will not use blue light so the actinics arn't really a contributor. Have you tested the output of your RO with a tds? Maybe you need a new membrane? the diatoms are taking up nutrients from the water, so cutting the lighting could help, but you need to eliminate the excess nutrients somehow.

Mike

you shoudl be fine with only 3-4 months, I have been using one for nearly a year and I have horrible water ranging from 600-1000 on the tds meter. Mine is nearing the end of its life now, so I doubt it is the membrane. how large is your bioload and what kind of skimmer do you use? also what is your feeding schedule?

everything sounds of to me, you may want to cut down on feeding a little until you eliminate the algae, but I definately don't think you are overfeeding, although I feed a lot less, once every 3 days, but all I have currently is a regal tang and sweetlips blenny in a 75. Seems like you've got a pretty good setup going there, so this may just be a fluke from a mini cycle or something. Adding a fuge with macroalgae in it would help too. I would just siphon it off and keep the flow high where it is growing, that should take care of it.
Mike