Low PH

[Squinchy]

So i'm having issues with a 680ish Gallon tank where the salinity dropped from 1.022 to 1.018 (due to the skimmer cup being plumed to the floor drain with a bit of a wet skimm draining the tank and the ATO refilling with fresh water)

So we dumped like 4 - 5 cups of salt in the sump to get the salinity up a bit and mixed the ATO water to around 1.035

the ph has dropped to around 4.5-5hp and the alk is around 12dkh

So my question is how do i correct the PH? can i use baking soda or will that also effect the alk?
or will soda ash be a better choice

 

[rayjay]

First thing to do is to have another method to check the pH, perhaps at your LFS. If it really WERE that low I doubt you would have any fish left alive. Just adding the salt to the sump should IN NO WAY affect a large drop in pH like that. If your pH is REALLY that low, you have a serious problem that needs more than baking soda/soda ash will cure.
I personally would have only mixed up a container of salt water to a higher s.g. and just slowly add it over a period of time, like you would get by your elevated level in the ATO. Dumping salt in the sump is likely to bring a sudden change in s.g. which sometimes can be harmful, much more so that the slowly decreasing s.g. you have experienced.
I believe baking soda will initially drop the pH and then bring it up while soda ash will initially tend to bring the pH higher and then settle down at the same level the baking soda would eventually do.

 

[mcgyvr]

Your pH test is not accurate..
Do you have sand in your tank? Is it rapidly dissolving? It would be if your pH was really that low..

Maybe you are reading alkalinity on the meq/l scale?

 

[bertoni]

I agree that pH at even 5 is too low to be possible. I would work on raising the SG slowly back to normal, and troubleshoot the pH kit or device. Anything you add to increase the pH will increase the alkalinity, and give only a temporary pH boost, in any case.