Spiral monti tissue loss overnight.

[BioBoy16]

Woke up this morning to see my monti slimming pretty bad. Didn't think much off it as my two spot blenny loves to just sit right on it. Thought he must have pissed it off. Went for my weekly water change and realized oh crap that's tissue loss. Not sure what happened it was doing great. Don't think it's nudis I've had it for months and the only recent addition was a cats paw I dipped. Any ideas?

 

Parameters:

 

Salinity: 1.025

Ph: holds pretty strong just north of 8

Alkalinity: around 8 but can dip towards the end of the week.

Calc: 415-445 holds strong just small frags in the tank.

Mag: 1253

 

Stocking: 4 blue leg hermits

1 astrea snail

2 nassari snails

peppermint shrimp

tail spot blenny

manadarin goby (spare me ive done the research and its doing just fine. Ive got walls covered in pods atm)

lettuce nudibranch

 

Unfortunately I've been using a FW kit for nitrates and I'm guessing it just doesn't even work. Experiencing cyno and GHA atm. Assuming its getting up there at this point. I use brightwell purit and a small refugium for nitrient export. Cut a big part of the cheato out to spur growth and replace my purit. Only things I dose are red sea ab+ and phyto. One every other day for recommended doeses. Tanks been running since November and only Experienced one coral death bc I acclimated it very very wrong. Learned freshwater dips on leathers are a very bad idea despite what i read lol. I keep up with my water changes. Totally unsure what started this except that maybe the nitrates/phosphates are building up. 

[empresto]

Certainly hard to say without a test kit reading for NO3 and PO4, though I would find it unlikely that your NO3 and PO4 being high would kill a montipora.  Mine grow better the higher nutrients go (within reason).  What will quickly wipe out SPS, including montis, is when NO3 and/or PO4 zero out.  Seeing as how you have a cheato fuge and you are seeing cyano and GHA, I'm going to guess PO4 is undetectable.  Get a couple good test kits for both (I use Hanna ULR Phosphorus and Red Sea Nitrate Pro test kits) and see what they say.

[BioBoy16]

Wow I didn't think of that thank you. I feed sparingly but now that I've gotten the mandarin I've been broadcast feeding can o cyclops. Little bugger is still afraid of me so I just turn the pumps off and swirl some around for him. I assumed everything jumped up from the additional feeding.