what can cause this?

[pkirby]

I have recently lost several sps corals. there are many that still look healthy... but they tend to start turning white at the base, and eventually working up until the coral is lost. One thing I've noticed recently is the coraline algae on the back wall of the tank is slowly turning white and going away... making me think the problem could be ph? I don't know of anything else that would make coraline dissolve?

I did have a period recently where my PH was testing 7.8, which is low... but I was able to get the PH back up by opening the window at night. I just received an order of soda lime so I can add a co2 scrubber, which should help keep my ph up where it belongs.

I tested water parameters today and got the following:
ph: 8.1
kh: 10
mg: 1300
cal: 520
Nitrate: 0
Phosphate: 0

Has anyone else seen this happen? 7.8 shouldn't be low enough to kill corals I wouldn't have thought... the other parameters look good to me

[MARINECRITTERS]

calcium is a bit to high for me.... but that's just me ( i like 440 ppm )

[pkirby]

I agree calcium is high... It is actually higher today than it was a week ago, and I haven't been dosing calcium. I'm thinking the coraline that seems to be dissolving is adding calcium back into the water?

[bnumair]

cal is high i like it 440 too but its probably not the reason. hows ur lighting? when where bulbs changed? if led did u acclimate the corals to ur lights?

[Reefin' Dude]

phosphate wicking up through the LR, then into the coral skeleton.

G~