Hair Algae & 15ppm of Nitrate

[b-town]

Hi everyone, This is my first message thread ever! But I need your help so here goes. I had a basic freshwater tank for 3 yrs with no problem. About 4 months ago i changed over to saltwater. I did a 3 week wait for the cycle and then added 3 small fish. From the 2nd week to 3rd week of the cycle i had brown algae that went away. Then it was clear and then the Hair Algae started about the 6th week and will not stop. Just want to know what you think about my set up and the cc bottom???
Tank:
55 gal all glass
cc bottom
1 CPR protein skimmer (works great)
1 Marineland Emperor 400 filter w/ Bio wheel
1 power head
Use 1 Algone pk a week in filter
PC light
My test results are always the same, they are: Sp Gravity 1.024, PH 8.0 -8.2, Calcium 350, temp 77-80, Ammonia 0, Nitrite 0, and Nitrate 15 to 20 ppm.
Why wont the Nitrate go down any???? And I have Hair algae all in the cc bed. I'll suck it out and then the next day its back!?!? I change the water 15 to 20 gals each week. I try to use RO water from the LFS but sometimes use tap water that i treat. I leave the lights on for only 1 hr or so a day and its still grows? I feed 1 time a day very little. Do I need more Equ. or a sand bed????????? I will be adding 50 lbs of live rook soon! I would love to hear what you think....
Peace

 

[scsinet]

Your nitrate levels don't explain the algae growth.
I'd be looking at phosphates right now. If you don't have a test kit, get one. Your water sources almost certainly point to phosphates as your problem. First, tap water almost always has unacceptable phosphate levels. You need to kick the habit of doing this immediately.
Second, if the LFS does not use a DI stage in their filter, or has not changed the resin lately, then their water may be high in phosphates also.
The good news is that phosphates can be easily removed by water changes (with phosphrate free water... of course), or by chemical media (but this should be a last resort).
Also, if I'm not mistaken, the emperor 400 has two bio wheels. Try removing one wheel, and see if that helps. Keep an eye on your ammonia levels while you do this. You may have an overpowered biofilter, which is producing nitrates too quickly.