Dumb Question About Ph.

So people told me to leave out tap water for the true pH. My tap water is 7.4-7.6 at first and when I leave it out it is 8.0.

8.0 is the closest to my tank water so my question is: do I have to let my tap water sit out for 24-48 hours EVERY SINGLE TIME for a water change for it to be 8.0?

Or is the tap water already 8.0 pH but only tests that number after sitting out for 24-48 hours.

 

Well, when I put water in my tank, I get some tap water, add a dechlorinator, and let it sit for a good 15-30 minutes, and then go ahead and dump it into the tank when ready.

Not sure if that's the right way to do it, but it's how I've been told to do it. I haven't heard anything about leaving the water out to get a different pH though.. I mean it's gonna hit 8 no matter what isn't it, regardless of whether it sits out or is in the tank?

 

Why would the PH change overtime. Chlorine and gases will be released but I don't think the PH should change. At least mine doesn't.

 

Why would the PH change overtime. Chlorine and gases will be released but I don't think the PH should change. At least mine doesn't.

The gases and chlorine released do change the pH in many instances, however like you mine doesn't.

 

You are correct. Didn't realize that. Also temperature of water changes the PH. Learned a lot about PH.

 

My pH does the same thing. Tap is 7.4 but after it gases off for 48 hours it's about 8.0 or 8.2. You likely have water that has high carbon dioxide. I was told this actually gives a false pH reading. Your true pH would be 8. You don't need to let it gas off each time unless you see your fish gulping for air (too much CO2).

It took me months to figure out the issue!

 

Mine does the opposite way. At first it looks like 7.4 or 7.6, but after awhile it goes down to 7.2

 

The key is how much water are you changing? The larger the tank and the smaller the % equals a tiny change in your overall ph. Doing a 90% water change will effect the ph a lot. Say your ph is 8, and tap water 7. If you do a 50% water change your tank should read 7.5 ph. Most fish can adjust to slight ph variations [under 1] without problems. I don't think you need to wait for tap water to change its ph with a normal [20%] water change. Of course monitor your fish to see if their effected.

 

The key is how much water are you changing? The larger the tank and the smaller the % equals a tiny change in your overall ph. Doing a 90% water change will effect the ph a lot. Say your ph is 8, and tap water 7. If you do a 50% water change your tank should read 7.5 ph. Most fish can adjust to slight ph variations [under 1] without problems. I don't think you need to wait for tap water to change its ph with a normal [20%] water change. Of course monitor your fish to see if their effected.

One would think that, right? If I change 25% my tank equals my tap water (drops from 8 or 8.2 to 7.4, which is my tap water). The math doesn't seem to work that way when CO2 is involved.