What's happening to my corals????

[KirstyMc]

Help needed please!!!!

A few weeks ago I found my acan frag on the sand bed with two of the polyps having been torn from the skeleton. Today I have found my frogspawn coral skeleton in the rock work where it's always been but the heads have somehow detached and are in the sand below despite appearing in good health yesterday. Has anyone got any ideas what could be causing this? I previously suspected my tuxedo urchin.

Stock is 2x Picasso clowns, mccoskers flasher wrasse, silver belly wrasse, purple firefish, sunspot goby with pistol shrimp, cleaner shrimp, conch, trochus snails, red leg hermits, red starfish (fromia?, feather duster worms, rock flower anemone.

My parameters are:
pH 8.0
Phosphate 0.03
Ammonia 0
Trite 0
Trate 0
Magnesium 1320
Calcium 470
Kh 11.5

My sg is normally 1.025 but when I've measured this morning it is 1.027 - unsure why - could this be a factor?

Any help greatly appreciated!

 

[JUNBUG361]

Pistol shrimp?? Maybe or bleaching out. Water evaporation causing the high salinity to reading. Do you ave a ATO with your system

 

[mcgyvr]

Your alkalinity is high..
7-11 is the recommended range..

What salt mix are you using?

 

[ReefEco]

Sounds like mechanical destruction, and fast - i.e. your Acans were fine one day, then on the sand bed the next? While some coral wasting can happen that fast, but I'd remove your shrimp and see if anything happens again. Under-fed shrimp are notorious for opening up corals, especially larger polyped corals, and trying to get food out of them. Alk is a tad high as well as salinity, so that could be it as well - but I would imagine those have been shifting gradually and corals would have shown similar gradual declines, rather than overnight destruction as you mention. Though some corals reach a tipping point and just go as well.

 

[KirstyMc]

I have an ATO but when I looked earlier I noticed that the sensor was way below the water level in the sump so I think I must have knocked it. I buy my water from my LFS, I'm not sure what salt they use but it is always 1.025 sg which is why I keep my sg at that level. Do you recommend I remove the pistol shrimp and the cleaner shrimp? Thanks for your help everyone.