silicates??

[wetone]

OK....I have some hair algae growing on my LR. I just added a Precision Marine Bullet 2 skimmer on Friday to replace my old counter current, so I know it will take a little time to effect anything with that (although its kicking out gunk already) I have 0 nitrates and phosphates in the tank, I only have 4 fish and hardly feed them,I have 2 250w MH on for 5 hrs a day and 2 110w VHO actinics on for 6 hrs a day. The tank is a 75g with 100 lbs of LR and a 40 gal sump with another30-50 lbs of LR and a 5" DSB in the sump. I cant figure out why this algae is growing,what nutrients could be there if the phos and NO3 are at 0?
I have heard about silicates from LFS, I have not tested, any thoughts or ideas???
Thanks

 

[wetone]

1 other thing I forgot.
I do have a Kent bare bone RO unit for top offs and water changes. The unit is 2 years old and I have never changed the filters inside, I still have no phos or nitrate reading in the RO freshwater either. Not like I want to spend another $250 bucks, but would a different unit, maybe RO/DI with a silicate filter be a better choice??

 

[wetone]

I'm using Salifert test kits. I test in the lowest range available per the instructions and the test results are totally clear!! Even asked my wife to confirm color readings and she agreed. I also had the water tested at LFS and they also found 0. My LFS did say that my TDS reading was around 415, which they thought was high and the new protein skimmer should lower that. I have a 75g tank and bought a skimmer rated for 250g!, I'm looking to nuke any bad stuff in there........