Toadstool coral (sarcophyton) became half white

[drdirkenstajn]

Hi Guys,

I have a problem with my toadstool coral. Before 3-4 weeks it becomes white on some places literally overnight and that was stable until and that remained unchanged until a few days ago when that whiteness began to spread. What is wrong?
I have mostly soft corals. The tank is old about 1 year.

Tank volume: 120 gallon
Nitrate (NO3): 0.3
Phosphate (PO4): 0
Temperature: 78F
Magnesium (Mg):1410
Calcium (Ca): 480
KH: 8.0
Salinity: 1.025

Please, help!
Marko

 

[SPR1968]

It might be worth moving it to a different position or changing the water flow around it to see if that helps