Ph Change After Water Change

[stanleo]

I did a 50% WC today. When I was done I did before and after tests. I tested the siphoned water in the bucket and I tested the water in the tank. Most of the tests came back the way you would expect but the ph is concerning. in the bucket it was 6.4 and in the tank it was 7.4. It has been five days since the last water change. My tap ph is 7.6. I do CO2 injection and the tap water  was dechlorinated. The fish don't seen effected yet but is there anything I should do? Its a new tank only set up at the beginning of August and I did a fishless cycle. I knew the ph would lower with the CO2 injection. I do 50% every 5 days because the diatoms and brown algae has been really bad but I think I am getting ahead of that. I am going to monitor the ph daily to track how fast it drops. I don't have a RO//DI unit. ANy advise is greatly appreciated.

 

[evan47]

the last couple of times i have tested my PH with the API test kit, i at first had readings of barely 6. i shook the solution bottle (which is in date but not used often) and lo and behold the reading was then my normal 7.4.
if you are really worried about your PH simply get another kit from a different manufacturer and compare results. 

 

[stanleo]

Thank you, I actually always shake my test bottles for 5 seconds before every use. The trick to testing is consistency. It's a couple hours and the fish are still behaving normally so it might be ok.

 

[Byron]

If I am understanding what you wrote correctly, it seems logical.  The tap water is 7.6, and the water taken from the tank prior to the change was 6.4, and after adding fresh tap water the pH ios 7.4.  In your situation, this is what I would expect.
 
The CO2 diffusion will lower the pH over the week.  You might want to do a smaller water change.
 
Byron.

 

[Ch4rlie]

Agreed with Byron said in his post.
 
Yes, thats is pretty much what i would expect as well, co2 and substrate as well as any rocks you may have, will all have an effect on pH over the course of a week.
 
Tap water 7.6
Fresh water in tank 7.4
 
Old tank water 6.4, lowered as a result of co2, rocks/substrate over time.
 
Nothing out of ordinary imho.
 
In my tank, my ph is generally 7.2 to 7.4 at end of week but out of tap, pH is nearer 8.0 to 8.2, and I did not run co2 at the time of those particular tank tests, but had a few pieces of bogwood, gravel substrate and light to moderately planted, as well as IAL and Rooibos tea. So all of these do have an effect, no two tank behaves the same in regards to ph, softness/hardness and water parameters.