tap water ph=6.6, tank ph=7.8 !?

After sitting out for 24 hours in a cup, my tap water ph went up from 6.6 to 7.8. I guess this means smaller, frequent pwc's are in order. :\

why? the rise in pH that you're seeing is likely from the off-gassing of CO2.
somebody correct me if I'm wrong, but the fish shouldn't even notice it...
 
Smaller, more frequent pwc's? Because doing a larger pwc will cause a big drop in tank ph at the time of the pwc.
 
your fish shouldn't even notice it....the rise in pH that you're seeing is due to offgassing and not due to a change in disolved solids in the water.

Note that I am not saying that you can change your pH willy-nilly by adding chemicals to the tank....that WILL affect your fish. Offgassing shouldn't....
 
I know that they are not going to notice the rising of the pH in the day following a water change. They WILL notice the drop in pH at the very moment I am doing a water change. I noticed this the other day when I did a 30% PWC. They were jetting across the tank for about 1.5hrs afterwards. This was the first PWC I've done since I finished cycling, and during the cycle was doing PWC's 1-2 times a day. I guess they never experienced that big of a pH drop during a PWC previously. Then again, when I've tested the water before, it was always around 7.5 which isn't much different. ^.- I was doing the PWC to start getting rid of cloudy meds and salt from the treatments I'd been doing for the past few weeks. Maybe the decrease in salt, meds, and pH all combined wigged them out a little.

I am going to get a large container to let my tap water sit in before water changes I think.
 
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it shouldnt effect the fish. keep up with the water changes. its like when i do water changes. the ph in my tank is lower because of the co2 i add. when i add the new the ph goes up and takes time before the co2 builds up and drops it again.

i think the effect of co2 dropping the ph doesnt effect the fish.
 
i would just leave it to sit in that big container, its also a good way to heat the water in the container to the same temp as the tank.
 
I have the exact same issue with my pH. Tap water pH is 6.8 and after sitting it rises to 7.6. I like to do weekly 50% water changes in my tanks, so I add a little baking soda to the water as I change it. Never had a problem yet. It instantly raises the pH and I can do as many water changes as necessary without worrying about pH fluctuations. For my 29 gallon, I add approx 1/2 tsp to the stream of water from my python. For my 10 gallon shrimp tank, I add about 1/8-1/4 tsp. I started doing this when I fishless cycled my tank and the pH began crashing due to my soft water. I experimented quite a bit without the fish in the tank so I could make sure there wouldn't be any issues with the different levels. I haven't had any problems and it also helps to keep my kH up as I have VERY soft water.
 
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