Tap Water pH off the scale!?

[Danny.]

Hi there, two weeks ago i did a 25% pwc for my 60g, all seemed well till afew days after when my fish started becoming lerthargic and staying motionless in the water, i wondered what the **** it was ran all tests, Ammonia 0, Nitrite 0, nitrate 20 nothing wrong so i tested the pH and it was off the scale acidic at about 4-5. I wondered how this could have happened so i tested my tap water and it was reading super acidic about pH 3-4, i bought another test kit to confirm this an API one tested the water and it the colour that came out couldnt even be matched upto the chart it was that acidic.
Im wondering what i can do? For a starts i dont think i shuld be drinking this water and secondly how do i change the water in my tank i have pH up crystals but they are quite expensive to be buying 2 packs every month also have got some API Proper pH 7 for free but on reading the instructrions you can't use it in tanks with live plants :/, i left it two weeks after i noticed to pH change too see if it would balance back out, usually its about 6.8-7.
Can anybody give me hand here because i really need to change some water any ideas?
Thanks

 

[cmor1701d]

Is this well water or municipal?
I doubt municipal water would be allowed to go that acidic.

You can use baking soda to increase pH. It's cheap, but use it sparingly, like a quarter teaspoon at a time to slowly raise the pH over a period of days.