ALK/PH swings killing fish?

[wsoldier]

I'm 4 months in and short of it all is most all my fish have died within about 10 days of each other. I didn't see any visible parasites and all looked healthy up until until this time, although some were only added to the tank 2 weeks before. After the first fish died, I realized that my ALK had lowered faster than I realized and I started dosing the towards the lower-mid recommended kalk in my ATO. I think the Red Sea test kit suggests not having swings of 1.4dkH per day for fish/coral health. Corals (mostly LPS) seem to have been okay. I should also note that I originally was running the ATO (with kalk) twice a day, but then moved to 3 times and shifted the times based on what I thought I could make it more stable.

Was the relatively quick rise in ALK on one day (from 5.32 to 9.8 in 3 days) enough to cause them all to stress, or were the swings just too great for either pH or ALK in general?

Oddly my inverts (skunk shrimp, tuxedo urchin, brittle star) have all survived thus far. Thanks in advance.

Salinity: 1.025
Nitrates: ~2 ppm
Phosphates: .02 ppm
Magnesium: 1500 (as of today)
Temp: 77

 

[Randy Holmes-Farley Verified Community Expert]

I doubt the alk changes killed the fish. The pH changes do not look outside the norm for many tanks.

 

[wsoldier]

I doubt the alk changes killed the fish. The pH changes do not look outside the norm for many tanks.

Thanks @Randy Holmes-Farley for the quick reply. I guess I'm really baffled about what happened then.

 

[piranhaman00]

Bump.

will doing large water that will cause dkh swing of about 2.0 dkh cause stress in a fish only tank?pH is the same

 

[Randy Holmes-Farley Verified Community Expert]

Bump.

will doing large water that will cause dkh swing of about 2.0 dkh cause stress in a fish only tank?pH is the same

How would you get that big of a swing? It would need to be a really big water change. A 20% change with 11 dkh water on a tank with 7 dKH only experiences a rise of 0.8 dKH.

As to stress, I'm not sure if fish care all that much about alkalinity itself.

 

[piranhaman00]

Tank is 7.0, new salt water is 11.0, 50-60% water change

 

[piranhaman00]

How would you get that big of a swing? It would need to be a really big water change. A 20% change with 11 dkh water on a tank with 7 dKH only experiences a rise of 0.8 dKH.

As to stress, I'm not sure if fish care all that much about alkalinity itself.

Above