Continuing pH issues

[David03]

My pH in my cycling tank continues to be around 7.5.

In the process of doing a water change, so I decided to see what the pH was in my brand new water... at an SG of 1.025, my pH in the new water is reading at 7.2-7.3.

I'm baffled, as I thought the water change water would be at pretty ideal parameters (8.3 or so).

Just to see if my probe is wrong I checked a couple of other things.

RO/DI water- 9.3

Tap water- 7.9

Is my probe out of wack? Or does this make sense?

 

[quarryshark]

May want to calibrate it to be sure. What salt mix are you using? Are you airating it before testing?

 

[David03]

I'm currently using Oceanic salt. And in terms of airation, I've got a powerhead in my 15 gallon bucket that I'm using for my water changes.

I'll be recalibrating the probe tonight, to make sure it is ok. Just got it a week and a half ago and calibrated it once, but will do it again.

 

[Phyl]

RO/DI has no buffering capacity to the PH in there will be all over the map and not very accurate (try shaking the glass to see what I mean). What brand of water do you use? Have you tried checking the Alk in that? You may find it to be low.

 

[quarryshark]

I'm currently using Oceanic salt.

I recently switch from Oceanic because of PH issues. I was getting reading of 7.9-8.0. May have something to do with it, but I doubt that the mix is as low as your readings.
Ya, try recalibrating and you may also want to take a sample to your LFS for verification of your readings.

 

[David03]

This evening I will retest all of my parameters, and see what I get, including Alk and Calcium. Have to say that my alk test, with a litmus type strip, isn't real easy to read... but I'll get you what I can.

And Phyllis, I use RO/DI water that comes from my tap, then through my unit that I purchased on ebay. Not sure of the brand.

Thanks again for all your assistance on this. I look forward to resolving this, so that I can stock!

 

[David03]

OK, here are my parameters (as best I know with my hard to read tests)


Temp. 79.7
SG 1.025
Amm. 0
Nitrite 0
Nitrate 0-5.0 (hard to tell, but closer to 0 I think)
pH 7.7
Alk 125 (2.5) (another that is hard to tell)
Calc 440-460

Note that over the past few days, I've pretty much used an entire bottle of buffer on the tank, and this is as high as it has read.

Thanks in advance for your input.
David