low pH - why?

fish_gal77

AC Members
Sep 13, 2005
90
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Orange County, CA
I posted a while back about a severe pH crash in my 44g tank... The consensus was that it suffered from 'old tank syndrome'. I performed several daily water changes and tested the water a LOT. At one point I had discovered little to no buffering capacity (0 deg KH) and added a tiny bit of baking soda so that the pH could at least hold and come slowly back up to my tap water level with the regular water changes. That was months ago now and I assumed I had everything sorted out. I hadn't added new fish because I was just so happy my angels survived and didn't want to chance any problems due to new fish. YES I know I should have a QT tank... but I don't.

I got a couple newbies this weekend and as I normally do when I get new fish, I tested the pH of the water they came in and tested the pH of my tank water. It's not as bad as it was during the crash (6.0 or less) but it is lower than normal - 7.2 ish. My tap water measures between 8.0-8.2. At that point I checked everything else:

Ammonia 0
Nitrites 0
Nitrates 10-20
KH 3 deg

So... what could be causing the pH shift??? I started using Prime water treatment after the crash incident a few months ago since my tap water has between up to 0.5ppm depending on the time of year (nitrites are 0 from the tap). I do not have any driftwood in the tank, all decor is fake and nothing new has been added in months! Could it be the Prime?
 
I think that most people will see about a point drop of ph after letting it sit out for a day, if that is the case in your situation, then your tank ph would be matching the tap ph.
 
I still wonder why the pH in the tank would be lower... Up until I had the pH crash/old tank syndrome issue, the tank pH always measured within .2 of the tap water (straight out of the tank). I just wonder what could have changed in my tank?
 
I still wonder why the pH in the tank would be lower... Up until I had the pH crash/old tank syndrome issue, the tank pH always measured within .2 of the tap water (straight out of the tank). I just wonder what could have changed in my tank?
are you adding any chemicals besides dechlor, or adding CO2?
 
I'm confused... it can take a day or 2 to show the true reading?

The sudden pH crash (and loss of 5 fish) happened in the summer... I performed daily water changes for a week and a half and then went to weekly changes. After I got all the levels sorted out, I didn't do regular water tests because I thought it would remain stable.
 
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