PH is my true problem

well I checked my PH again today.. and it is down at 5 once again.. this is getting very frustrating.. I did another 30% water change.. my ammonia was at .1 my nitrites at .1 as well.. every where I read it says that fish will die at a PH of 5 so why are mine still alive?? Does anyone please have some advice on what to do to raise the PH?? Everywhere I read people have probs with it being too high not too low..
thanks.. I have recently added co2 but it was low before that as well...

 

I don't know why your PH is so low, but I know of two ways to raise PH.

1.)Add some crushed coral to you substrate.

2.)They sell this chemical to raise or lower your PH. You can try and use that.