maze coral problem?

[Caramel]

I go a beautifil brain coral about 3 month ago. After a couple of days, I noticed there was some white spot on the coral flesh that looked like decaying flesh (small area). I gave it a iodine bath nd the white disapeared leaving the skeleton bare at this spot.
I'm not sure it is related to that but it's been now 3 weeks I coulod notice the fleash receding at this place.
My water parameters are okay, Ca 470 ppm, alk 6.4 dKH, pH 8.1, no N, PO4 always been ~0.2 ppm, Mg ~1270 ppm.
The other corals (SPS, LPS and Soft) are fine. However, 1 of the frogspawn also have flesh receding from the foot but seems to stabilize.

Any input on what can be causing this and how to cure it?

Thanks!

[theplatypus]

Your dKH seems a little low for Ca of 470, but nothing major. Where are you keeping it in your tank in regards to flow and light?

[theplatypus]

The more I think about it your dKH seems a lot low. But I'll let one of the chemistry gurus chime in on that.

[Caramel]

Agreed, it looks low to me too. However, I looked at a post from Tom (this guy seems to be Dr of water chemistry): http://www.thereeftank.com/forums/f6...ght=alkalinity
and the table shows that at pH 8.1 with a alk of 6.4 dKH you still get a good PCO2. I'm planning to do a water change tomorrow, measure it again and adjust with reef builder (seachem). I think may be my coraline (that grows like creazy) is consumming the Alk.
Do you think that could be why the brain has problem?
My lamp is MH 10K, 150W and 2 actinic 65W.
The coral is close to the sand.

Originally Posted by theplatypus

The more I think about it your dKH seems a lot low. But I'll let one of the chemistry gurus chime in on that.

[theplatypus]

Originally Posted by Caramel

Agreed, it looks low to me too. However, I looked at a post from Tom (this guy seems to be Dr of water chemistry): http://www.thereeftank.com/forums/f6...ght=alkalinity
and the table shows that at pH 8.1 with a alk of 6.4 dKH you still get a good PCO2. I'm planning to do a water change tomorrow, measure it again and adjust with reef builder (seachem). I think may be my coraline (that grows like creazy) is consumming the Alk.
Do you think that could be why the brain has problem?
My lamp is MH 10K, 150W and 2 actinic 65W.
The coral is close to the sand.

Tom certainly knows his stuff and I would defer to him on just about every aspect of reef keeping. What kits are you using to test for pH,Ca,dKH, and Mg? When are you testing pH?

[Caramel]

I'm using the Salifer kits and I test pH once in a while with the other parameters. Morning or evening, doesn't really matter since I have a fuge with light on 24/24.

Originally Posted by theplatypus

Tom certainly knows his stuff and I would defer to him on just about every aspect of reef keeping. What kits are you using to test for pH,Ca,dKH, and Mg? When are you testing pH?