What happened to my happy Acan lord?

[JoJosReef]

This was my acan last week:

It has been looking even better since then; plump, fleshy and colorful. Target fed it reef roids this AM then came home to it looking like this:

See how two left lobes look shredded?

Haven't had a chance to check parameters yet, but last check 2 days ago was:
Temp: 77
NH3: 0.25 (API, equals nada)
NO2: 0
NO3: ~2.5 (API)
Alk: 11.5 (Salifert)
Ca: 430 (Salifert)
Mg: 1250 (Salifert)

Salinity has been holding stable at 1.026, also this AM when I checked at feed. Last reef roid feeding was a week ago.

I have a wily dwarf blue leg hermit that I've seen crawling over the GSP and Zoa before. Could he be the culprit? Or was the reef roids an overdose?

Thank you!

 

[Nigel35]

How about those phosphates? Also it would help to know what kind of inhabitants you have in your tank?

 

[JoJosReef]

Thanks! I am still interested in solving this!

Just got my first phosphate test kit from BRS today and tested it before I did a WC. Salifert--my best guess is 0.25, but it was pretty light so it could have been the next level down.

Did another round of tests at the same time. Everything else stable, except Alkalinity, which rose to 12.65 from 11.5 (always +/-, because that last drop is always a "Did I need that last drop? or, Did I need one more drop?").

Worse news, during the water change, looks like the flesh of those two lobes sloughed off--I still have it in there hoping the third lobe makes it through, but it doesn't look pretty.

RE: livestock:
2x ocellaris clownpigs
1x Fire cleaner shrimp
1x missing hi fin goby (likely dead)
1x missing Randall's pistol shrimp super small (likely dead)
1x Fighting conch
1x Dwarf blue leg hermit
1x Nassarius vibex
6x Trochus snails
~6x dwarf cerith snails
1x Rainbow BTA
1x Duncan
1x Alveopora
1x Dragon eyes zoa with 4ish polyps
1x green acan lord (really micromussa?)
1x red/blue acan lord (the one in critical)

Just added tonight after water change--all after the acan lord went into critical:
1x hammer
2x candy canes
1x FL ricordea
1x blastomussa
1x mixed zoa with 3 polyps

 

[blaxsun]

This looks like the remnants of my acans after my midnight dwarf angelfish made a late evening buffet of them.

 

[JoJosReef]

Possible it would be the hermit? I don't think it would be the cleaner shrimp. I target feed him/her plenty. The hermit worries me because I don't have any GHA yet, but I tend to overfeed pellets and drop algae wafers or clip nori every now and then...

 

[JoJosReef]

Livestock update: after weeks of being presumed dead, I found the pistol shrimp just this am. Saw some sand get shot out of a crevice below the main rock structure and was able to shine a light inside and confirm the presence of the shrimp. It looks like he's made a huge cavern below the main rock (could the goby be there with him?)

Anyway, would a very small pistol shrimp leave the cavern and venture up the rock to eat the acan? Doubtful, but anyone have experience with that?