Lights or Diatoms ????

[Rustafar]

Hey everybody, I'm having a problem with diatoms, I think.
I recently re setup my 55 gal tank. Before it was a reef tank I had for 5 yrs,W/ MHs. soft corals, anems . Anyway after a few days I started getting the dreaded diatoms. It's been a couple of months now and it seems to continue.
I'm using RO water. My ammonia is 0, nitrites 0 but my nitrates are high. 40 to 50 on API test kit I'm adding Biozyme for added bacteria,using a nitrate filter pad,doing 20 gal water changes every two weeks and still blooming.
I also cleaned out my sump and bioballs.
The lights I have is a Oddysea 4 bulb T5 fixture with stock bulbs, I know it's not a very good fixture but It's all I got right now.
Any help with this problem is much appreciated.
Here's a couple of vids.
Russ.
Before cleaning:
http://www.youtube.com/watch?v=sCZWx0x00_k

After Cleaning:
http://www.youtube.com/watch?v=S3XPdLUpwrE

[cubalz]

Your tank is still new and needs to finish cycling. Your water has not had time to age. The only way to get rid of nitrates is through water changes. If I were you: start doing 10% water changes every week, limit the amount of food you are giving to the fish and cut back on the length of time the lights are on. You really should tell us how many fish are in your tank too.

[Rustafar]

Thanks for the reply cubalz.
Right now I have a 5yr old sailfin tang, (yes I know bit big for a 55 gal). Had him since he was about 2 1/2 -3 inches. Friendly "little" dude. might see if my LFS wants him.
3 damsels, half dozen hermits, a couple of snails, had more, but the nitrates got them.
At first I had a LED fixture on it but changed to T5s. Thought the leds were the problem (growing Algae). Obviously not. The brown stuff is coming back again.
I cut the lights down from 8 hrs to 4 hrs yesterday. I feed a pinch of marine flake in the mornings and small amount of frozen brine in the evenings.The tang grazes on rocks during the day. ( but not enough ) Doing a WC today.
It's funny that this never happened when I first set the tank up yrs ago. Oh well.
Patience is a virtue.
Thanks for your input, much appreciated.

[RUGDOG]

If you did not already you should get rid of bio balls altogether. They tend to trap and keep nitrates up.