Alkalinity dropping slowly...normal?

[sdergar]

I just did my weekly water testing today and found that over the last month and a bit that my alkalinity is dropping while my PH was staying steady at 8.2. I was under the impression that alkalinity and PH were tied together. Is there anything I should do to raise the alk? I'm using the red reef test kit and the scale shows me that I'm on the low side 2.0.

Parameters are:

SG 1.025
PH 8.2
Alk 2.0
Cal 420
Ammonia 0
Nitrite 0
Nitrate 0

The tank has been up and running since October of 2010 with mostly LPS corals, and 5 fish, CUC, etc. (120g)

Is this normal? Also I found that changing 20gal every two weeks seems to keep everything in check. I test right before and then 24-48 hrs after the pwc and all remains the same except as stated above for the alk in the last month & a bit. Thanks...

Steve

 

[cmor1701d]

Have you tested the salt water mix before a pwc to check Alk, Ca, and Mg?
A regular pwc should keep the levels in check unless you have a large load that is using it. I would expect the Ca to be affected more.

I had a problem with Kent salt mix a few years ago on 2 buckets. Kent confirmed the problem from samples I sent them and sent some buffer.

So start. With checking the salt mix and work from there.

 

[sdergar]

No I haven't. Actually I'm just mixing up a batch for the QT tank. I'll do some testing on that. Thanks for the tip Cmor...

Steve

 

[Floyd R Turbo]

Also it could be your test kit. Before making any adjustments, which could do more harm, I'd find someone that can test your water with a different brand of test kit.