Help with SPS death.

[michika]

I'm am at the end of my proverbial rope, and I need as many suggestions as you can offer me to try and get things right again.

The quick version of my tank's history;
- Set up in late November, moved all my livestock over from my 24g cube.
- By the beginning of December all of my SPS, and most of my LPS were dead, RTN, or just wasting away. This death also included all but two of my clams. All fish and inverts survived.
- Ran the system until January without any frags. I saw a bloom in GHA and made changes to the system.
- Added frags in January, saw growth and color changes for quite some time
- Early February; removed some rocks with GHA, and added more rocks to the sump, began to see RTN.

All the most recent RTNs were frags from the same source until a couple of days ago. Now the RTN is not discriminating. Some frags RTN from the base, and others from the tips. Today there is no polyp extension on any SPS frags still living.

Parameters from the 11th;
SG: 1.025 (today)
pH: 8.1 (before lights on, same as lights on though)
Ca: 420 (today)
Mg: 1190
dKH: 7, cusp of 8 (today)
Phos: 0.01
Nitrate: 0ppm (today)
Nitrite: 0
Amm: 0
temp: 80.1 (today)

The tank has approximately 60g total volume. I guess that I have approximately 60lbs total of rock in the system. I am currently trying to add in more live rock to the display.

- I try for 1-2 7g water changes a week with Ocean Pure Pro salt.
- I feed a small amount everyday, mostly for the chromis.
- My bulbs are all relatively new, within the last 2-3 weeks.
- My lighting runs 11am-8pm, 1x 175w MH SE XM 15K bulb and 2x actinic PC bulbs.
- I skim heavily
- Flow is a Snapper pump divided into a calfo manifold. I also have a hydor koralia 1 in the system in case of power failure.
- I run a kalk reactor, I run my top off water through it.
- I run a Ca. reactor, new media added in December.
- I also run a phosban reactor with phosban, and I run carbon as well (both changed out recently)
- I only use RO/DI water

I am also not seeing any coraline algae growth in this tank at all, either on rocks, or on the glass. I miss keeping SPS and I really want to try and sort this out asap.

So suggest away please!