SPS die in 60G cube

[siskiou]

I don;t know if anyone remembers, but last December, I had a strange event happening in my 60G cube (water turned pink, corals unhappy, then seemingly things recovered after massive water changes, carbon etc.).

 

Ever since, I can't keep sps corals alive in that tank.

They start out doing great and even grow a little, but then slowly start dieing from the tips down.

If I take the coral out when there is still sufficient tissue alive and put the in my 120G, they recover and do well again.

 

All softies and LPS, fish, snails, crabs are doing fine in the tank, and parameters check out fine, but it's a death trap for sps.

 

Does anyone have any ideas what the cause could be, and what I could test for that's beyond the usual tests (ammonia, nitrite/trate, calcium, alk, magnesium, phosphates, temp, pH)?

 

The only other thing I have changed since is the MH bulb, but the issue was happening before then.

[andy]

Tip-down problems are a common symptom of alk problems (either high alk, or too-rapid swings from low to high). How are you dosing calcium and carbonate?

 

Also, do you have a controller? If so, what is your typical pH swing over the course of a day?

[siskiou]

I have a calcium reactor on a pH controller on the tank, though since there are no longer any sps corals in the tank, I'll probably take that off soon.

 

pH is between 8-8.2, alk is at 10.

[Lowman]

Check your bulb carefully for cracks

[siskiou]

I thought that might be the problem, and that's why I changed out the bulb.

The new bulb definitely doesn't have any cracks (the old one was kind of milky looking), but it's been a few months, and things have not improved.