Mysterious Coral deaths

[Brizee1234]

Over the past 3 months I have been losing corals species by species. All colonies of the same species start to show tissue loss within a week of each other in all locations around the tank. So far it has hit all of my Turbinaria and Echinopora These corals have been in this tank for over 5 years and have grown and were well established. Most recently my Acropora have started bleaching from the tips. Has anyone seen this before?

I haven't changed anything on this system for years, however pH has been running on the low side recently (hovering around 8.0).

pH: 8.0
Alkalinity: 3-3.5 mEq/L
Salinity: 32.5 ppt
Ammonia: 0
Nitrate: 10 ppm
Nitrite: .02 ppm
Phosphate: 0
Calcium 440 ppm
Magnesium 1250 ppm

I have a GFO reactor, Carbon reactor and calcium reactor.

Does anyone have any thoughts? I'm assuming it is something water quality related since it is affecting corals all over the tank.

 

[jorwill]

very low salinity

 

[elysics]

Burnt acro tips from the combination of low phosphate and high alkalinity.

What are you measuring phosphate with? Is it actually 0? Because no phosphate at all would be a reason why corals die