Acropora STN?

[dunc101]

Hey guys,
I am new to SPS corals and one of my Acropora is starting to "bleach" from the tips and some stringy "tissue" (I think at least) is coming out of all of the polyp holes in the coral. It has been getting slowly worse of the past couple of weeks. It has been in the tank for around 1 month.
Below is a picture.

Could someone confirm if this is STN, please? If it is, what is my best course of action?

Thanks!

 

[KJAhp098]

Looks like STN. Possibly phosphates from the looks of the brown color. Can you post your tank parameters, lighting and other equipment?

 

[dunc101]

Looks like STN. Possibly phosphates from the looks of the brown color. Can you post your tank parameters, lighting and other equipment?

Sure.

90 gallon mixed...30 gallon sump with Reef Octopus XS 160 skimmer.
T5 x6 54 watt lighting currently running:
- 2 uvl purple
- 1 ati aqualblue
- 1 Giesemann Aqua blue plus
- 2 GE 6500

I am replacing these bulbs this weekend with 4 x ATI blue plus, 1 ATI purple plus, and 1 GE 6500. The bulbs I am currenlty running is currently too white for my taste...

It is currently my hunch of why this coral could be so brown as it sits at the top of the tank under both of the GE 6500k bulbs. When I got it, it was more of a teal green.

I added another acro the same day as I added this one and it seems to be doing well with good polyp extension. I have never seen any polyp extension with the coral pictured above.

Water parameters:
ammonia: 0
nitrite: 0
nitrate: 0 - 5
Phosphate: 0 - .25 and I am not having any issues with nuisance algae.
dKH: 11
Calcium: 460

Thanks for the help!

 

[MammothReefer]

.25 is a bit high for SPS

 

[karsseboom]

wow .25 p04? thats pretty high.