Ph Problem

Yes, it's me again with another axy problem/question. Can't seem to get a break lately! Anyways my master liquid test kit came in today (I had test strips before) and I tested my tank water and the ph is 6! What?! I was shocked because our tap water sits right around 7.5. My test strips didn't test ph but I knew the tap was 7.5 so I didn't really worry about the ph. I know 6 is really low for them. Now I'm worried about doing water changes from tap water because this will raise the ph quickly and I definetly don't want that but I don't want them in that kind of acidic water! I know shells will raise the ph but can you just crush your own shells and clean that and use it, or does it need to be store bought shell grit? What kind of damage will low ph do to axolotls? Will they be okay in there until I get some form of shell grit? Also what could cause such a drastic decrease in ph from the tap to the tank? Helps appreciated!

6 isn't that bad. If they've been fine until now, keep doing what you're doing. Sometimes ignorance is bliss!

I know when i was cycling my tank, the PH had dropped to 6 and it made my cycle crash as it started killing the 'good bacteria'
I bought a cheap bag of crushed oyster shell (bird grit) off ebay for around £2 and made a 'stone' the size of my hand, it raised the ph to 6.8/7 and ive got more than half the bag still left for the future
I assume you could just crush your own as thats all the retailers do, just research which shell is best for raising ph.

Yeah I think the axolotls were about as aware of the low ph as I was. It really doesn't seem to be bothering them. I think I'll get some shell grit or crush my own just to be safe, but at least it's not hurting them right now!