STN causes

[JohnCisco]

Current parameters
1.026
Alk 10.4 (Hannah)
Calcium 440 (Red Sea)
Mag 1430 (Red Sea)
Phosphate 0 (Hanna ULR) (recently down from 0.03)
Nitrate between 5 and 12, closer to 12 (Nyos) (down from 25-50 2 months prior)
PH 8.0-8.1
Temp 77-78

180 gallon tank with 100 gallon sump (not rubbermaid brand but same material)
MP40 and 2 xf250 gyres
Barracuda gold return pump from basement... about 1,500 gph into the display
2 Kessil AP700s and T5s

Coral Beauty Angelfish, Magnificent FoxFace, 2 clown, 1 cleaner shrimp, 3 anthias, yellow tang, 9 rose BTAs

Tank was setup end of December 2018. I added some softies from another tank after 3+ months, fish after cycle, etc. No issues with fish or inverts.

I bought some SPS frags (red digi, birdnest, purple stylo) in October. They very quickly developed "bald" spots on them and eventually STN. The red digi (10-12 weeks now) is down to just a dozen polyps. The purple stylo photo attached below.

Talking with a few people they thought my magnesium was too low and my nitrates were way too high. This was 4 weeks ago or so. Mag was 1360, raised to 1430. Nitrates were 25-50 and I started dosing NOPOX to reduce them.

The purple stylo looks much better since then.

I got 3 more frags more as a test to see how a healthy frag responds to the tank. A green digi, a hydnophora, and a red setosa.
It's been 5 days, the green digi is getting "spots" like the previous corals did. The hydnophora and setosa seem to be ok so far but polyp extension isn't great.

What would be causing this? Is it stress from moving to a new tank or is this indicative of something else? That's my main question is someone with a lot of SPS knowledge see this picture and say XYZ causes this? I know 0 phosphates isn't good but I'm trying to get a hold of the nitrates and am starting to feed my fish more heavily. Acans, chalices, zoas, mushrooms... they all look fine.

The green digi with the "balding" spots and the purple stylo are attached. I took the pictures this morning with the lights out, just ambient light in the room as it was easier to see what I mean on the green digi. The digi came out of a tank where it grows like a weed, it within 6" of the top of the water with radions on the tank.

thoughts?

Aside from the nitrates being high...and now phosphates being low, I'm not sure. I've never seen my fish pick at any of the corals.
If this is a nitrate issue, getting them down further (closer to 5) should the frags rebound and be fine?

 

[Charlie’s Frags]

Nopox caused stn on all my sps.
I recommend growing chaeto if you’re trying to reduce no3. I know plenty of high end sps collectors that keep their no3 between 10-25, me included, so I wouldn’t worry about them unless they are getting close to 50. Stop the nopox and reduce your skimmer to 12 hours until you get some po4. Po4 needs to be 0.08-0.12 for sps frags. I only run my skimmer at night when the lights are off.

 

[JohnCisco]

So this same thing happened previously before I was dosing Nopox ... but my nitrates were between 25 and 50 (hard to tell on the colors but closer to 50) and the magnesium was 1360. This was then when I talked with someone knowledgeable and they said to first raise mag and reduce nitrates that it could cause this.

Could either of those things cause the same symptoms? And thus in trying to remedy that I'm creating the same symptoms but from a different cause?

I have chaeto, it's just not consuming the nitrates quick enough apparently. It doesn't grow a whole lot, I've got a kessil H380 on it. But it's been in there 5 months and doesn't do much. Lights are on 14 hours a day. Came out of a different tank with a different light, figured it needed some time to adjust to the light...

I haven't seen anything nip the corals, but could it be the coral beauty and I just haven't seen him do it? I guess the only way to know for sure would be to catch him and see if it goes away.

 

[Charlie’s Frags]

Didn’t notice your high Alk. Alk is way too high for 0.03 po4 and nopox. Your alk should be around 8 with po4 that low. I would do some massive water changes with a lower alk salt. This will also bring your no3 down. Try getting your po4 up to 0.08. You could even dose po4. I don’t like nopox but read the side of your bottle.