Is this caused by Dino or Diatom?

[daniellegui1206]

Hi there,

I need some help to ID what's the issue with my tank. It is killing the SPS and LPS. My duncan was happy until two weeks ago - most of the heads are gone now. Below are the pics of the corals that are impacted most.

The specs of the tank are:
Calcium 1350
Alk 8.0-8.3
Ph 7.8-8
Nitrate 13
Phosphate 0.08

Several weeks ago, I used AIPTASIA-X to treat Aiptasia issue, not sure if the solution would have any side effect.

 

[homer1475]

Calcium 1350?

Hope thats a typo, as I don't even think thats possible.

And how old is this tank?