As long as you keep only axolotl and no other companions (ie no feeder fish/snails etc) in it and your axie doesn't get too large (they can grow to 32cm+) depending on feeding/water quality conditions.
You may find in summer that this size tank will heat up faster, smaller tanks to, than a larger. If you intend getting another axolotl your tank needs to be at least 80-90cm long x 30-35cm wide.
How big are the glass stones? If they're about 2-3cm in size, remove them. Our adults had been on glass pebbles of this size and managed to swallow them (they do not regurgitate them) and excreted them over a period of almost 2 years. Basically substrate (gravel/rocks/pebbles) that is smaller than an adult axolotls head should be removed they can be swallowed. If you don't then your axie can at best manage to excrete them all out over a period of months or at worst have severe blockage/impaction leading to a prolapse and eventual death - one of ours died after a prolapse and a glass pebble half out of its cloaca region.
Did you cycle your tank?
http://www.caudata.org/cc/articles/cyclingEDK.shtml
http://www.caudata.org/cc/articles/waterquality.shtml
What other chemicals are you using in your tank?
If you don't already have one invest in a turkey baster = these are great spotcleaners (cleans up uneaten food/waste etc...); as well as freshwater test kits for ammonia, nitrite and nitrates. The best test kits to buy are the test tube kind (don't buy the dip strip/paper tabs ones they're harder to work out and aren't as accurate as the test tube liquid drop ones). These tests will help you determine when the tank is cycled and also once it is cycled if you ever have a water quality problem.
Do you have a filter - if you do make sure you don't clean it at all during the next 4-8 weeks as the good bacteria will establish itself on the filter media. If you don't, your waterchanges (once it is cycled will need to be done twice a week rather than weekly). Check out the following links regarding filters:
http://www.caudata.org/cc/articles/filters.shtml
If your tank wasn't cycled then do partial waterchanges daily (only 20%) or every few days for several weeks. This will allow your tank to cycle (establish good bacteria that aids the tank in cleaning) as well as keep any toxins down in the water and keep it relatively safe for your axie. Don't be tempted to add any chemicals to the tank (that the petshop suggests) to help/fix/cycle the tank as it won't = the partial waterchanges will sort things out.
EDIT : Once again Bellabelloo beats me to it