Odd Die off in tank

[makeshift101]

So I noticed oen of my Acropora have a lot of die off, like almost completely dead in a matter of a week.

Then I notices some of my polyps have disspeared along with some zoas
With this white stuff covering them

The only thing that i changed was added biopellets. I only added about 50 gallons with in my 120, and it ran for only a week.

I moved a powerhead a while ago and it was suggested to me that that could have caused the die off if it didnt have flow, but my whole tank is pretty much flow, i moved it back and havent seen much change,

Also, my skimmer has been going crazy, though that could be it finally starting to work properly

Alk 5.4
calcium 450
mag 1150
nitrates 1.5-2
po4 0

any suggestions would be helpful

 

[makeshift101]

and to add, all my other sps and zoas have been fine, no change

 

[Mr D smack]

Mag and alk are low. Raise the mag before anything else

 

[Scubareefman]

Pali's pull up sand to add mass, however the state of the polyps that are regressing looks like sundial snail damage to me. I would pull it and dip it, look at the bottom of the frag/rock for tiny (really tiny) snails. I have had the same damage in the past due to sundials, the good news is they don't breed fast and are not that great at hiding and don't travel far from the food (polyps) they are feeding on.

 

[Pife]

So I noticed oen of my Acropora have a lot of die off, like almost completely dead in a matter of a week.

Then I notices some of my polyps have disspeared along with some zoas
With this white stuff covering them

The only thing that i changed was added biopellets. I only added about 50 gallons with in my 120, and it ran for only a week.

I moved a powerhead a while ago and it was suggested to me that that could have caused the die off if it didnt have flow, but my whole tank is pretty much flow, i moved it back and havent seen much change,

Also, my skimmer has been going crazy, though that could be it finally starting to work properly

Alk 5.4
calcium 450
mag 1150
nitrates 1.5-2
po4 0

any suggestions would be helpful

If you Alk is really that low that explains all of it. I agree with DSmack, get your mag up and then get everything else in check.

 

[makeshift101]

Working on getting everything up now, then well see