water PH levels

Question
Hi,
The water in our 10 gallon tank has a PH level around 6 - 6.2. I have tried PH increase to try to raise it a bit but no luck. When I test the PH of the tap water it is around 7.  Even when replace about 50% of the water in the tank, the PH remains around 6.2
What in the tank would make the water PH drop?  What can I do to raise the PH? We have had a few fish die mainly catfish and I think that it might be due to the PH level.

Answer
Shane,
there may be alot of debis built up in the gravel bed that can cause this to happen.
filters may need cleaning as well.
you can raise the ph with ph block or liquid however I would rather you locate water that has the ph that you are looking for right out of the tap.
6.8-7.2 is about where you want to land with this, the problem with buffers is that once they get used up the ph reverts back to its original state.
I would clean the gravel well first, then the filters a couple of days after.
if you can locate some spring water etc not the store bought stuff.
that usually has a higher ph around 7.2-7.4 that would work just fine as water tends to head to the acidic the older it gets.
good luck!