Looking for advice please! Alk spike

ValG · Apr 5, 2016

So i keep my alk at around 7.8 - 8.2 on my LPS/zoa 60 gallon frag tank. I did a water change last night of 15 gallons = roughly 25%. This morning all snails/hermit are dead. All corals completely closed up: euphillias, zoas, blastos, etc. Checked ammonia and it was between 0.00 and 0.25 based on API test kit. Added some ammonia detox per bottles instructions and off to work. Asked my wife to keep an eye on things. Got back and ran through all the following test:
API:
Ammonia still between 0.00 and .025
Ph - 8.2
Nitrite - 0.00
Nitrates 0.00
Red Sea
Ca - 410
Alk 11!!!!!
I did not test the salt water before WC it was out of the new box and then i dosed (by hand)my regular amount of two part for both Ca and Alk.
Now to my questions: Are all my corals totally toast? Should I attempt to lower Alk if yes what's the safe level to drop it by? What's the plan of action? I don't think it's a goof idea to move coral into a different tank, where Alk is right around 8.00.
Thanks in advance!!

Randy Holmes-Farley · Apr 5, 2016

I don't think it likely that the alk rise (even if real) killed those organisms.

Did you use tap water?

While a 3 dKH rise can be stressful for corals, I cannot see it hurting hermits, and 11 dKH in general is fine for a reef tank that is not a ULNS SPS tank.

ValG · Apr 5, 2016

Thank you for your response Randy! I used RO water to mix with TDS reading at 000.
The corals don't look like they are dying yet but definitely very stressed. Not quite sure what caused the snail/hermits deaths. Over the last couple of weeks there has been some white stringy "algae" growing in that tank that I was syphoning out pretty much daily. After doing some readings online the only thing that I found similar to what I had was the "white reef slime", article from coral magazine.
I am mixing another batch of slat water and will test it before doing any water changes. Is it a good idea to do a water change right now at all? I guess my goal would be to lower Alk level a bit in hope to relief of the stress from the corals.

Randy Holmes-Farley · Apr 6, 2016

What salt mix are you using?
It's hard to know if a water change will help or hurt without knowing what the problem is and whether the new water brought it.

All you can do is try, I guess.

Not sure how you'd lower the alk level by water change alone since most mixes have about what your tank has. 11 dKH is definitely OK in general. I usually recommend 7-11 dKH for reef tanks. You can lower it with acid, but I wouldn't recommend that.