2 Questions that need answering

[CharlieBB]

Hi Guys,
Got a few questions for you.
My tank 2ft cube (SPS) is having somewhat of an algae out break. It started with green slime over the glass, which has now mostly gone. But cyano has taken over my sand bed, and is moving close to my rocks. I'm wondering what I can do to rid my tank of it?
The tank is about 6 months old, and I run 6 24 W t5's ATI. I dose the usual CA, MG and Alk but in adition I use Coral Vitalizer, B Balance, K Balance and Coral Snow, however I've stoped using all except for K Bal and Coral Snow. I top up with RO and I water change with NSW mostly.
Can anyone help me out?
And also I seem to have lost alot of polyp extension in my acropora aspera and I'm wondering how that can change?
Thanks

[robs.mark]

What are your parameters? sounds like it could be a p04 issue..

[CharlieBB]

I had suspected as much, my po4 is a kittle elevated, but not overly, it's sitting at about 0.06.
What can I do to combat the cyano? I've been doing water changes and trying to syphon, is that all I can do?
Thanks

[napsterMS]

The phosphate can appear to be low in a tank but the algae is using it all up before you test. I would test your rodi water with a tds meter and if it is too high then replace your filters.