Frog, those pH levels are fine for axolotls, they are ok in pH ranges from 6.4-8.0. Saying that if you have any ammonia at all in your tank/tubs and the pH is at the higher end of the scale 8.0+ then your ammonia becomes far more toxic. So, I wouldn't bother getting driftwood, if I was you. Only if it veers out of the range I've given you, then there are other ways you can raise or lower (ie peat being one I think to lower pH, bird grit in a stocking/shells to raise the pH - I've never had a problem - our tanks range between pH 7.2-7.8)