any idea for increasing pH?

I'm sure you don't. But it's worth mentioning from time to time why water softeners (and API's "water softening pillow" which works exactly the same way and scandalously is flogged as an aid to keeping low TDS fish) are a Bad Thing.
 
I'm sure you don't. But it's worth mentioning from time to time why water softeners (and API's "water softening pillow" which works exactly the same way and scandalously is flogged as an aid to keeping low TDS fish) are a Bad Thing.

Same thing goes for distilled water which I used to use...luckily I didn't learn the hard way...
 
if there are no fish in the tank (is it being cycled right now?) i don't see a need to deal with the pH just yet. it may be possible that part of the acidity is related to an overabundance of nitrate or something else to do with the cycle.

do some tests so this can be figured out. this is why you need your own test kits.

ammonia - ?
nitrite - ?
nitrate - ?
pH of water right out of tap - ?
pH of water after letting the sample sit out overnight - ?
 
Wouldn't touch it with a barge pole. It'll lower pH, but that does very little for the fish. What matters is getting the TDS reduced.
 
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