Okay. You did state that you didn't want heartbreak again. The sand suggestion is a recommendation of this site - final decision is ultimately up to you. As far as already having sand in the tank, sure, that's fine. Air stones stress some axolotls and aren't really needed. Some use them because they like the look, or to aid in evaporation (lowers tank temp sometimes).
Personally, I would stop using the safe balance. Axolotls can adjust to a wide range of pH and it is better for them to adjust to your normal pH, rather than you to use chemicals to adjust the pH. Aquarium salt use will get you a mixed bag of opinions. Breeders have told me that they use salt in their tanks. I refrain from it because my pH is already on the high side (7.6 - 7.8) so I don't want to raise it further. You may want to take that into consideration depending on your normal pH.
So you are using safe balance and nitraban? Isn't that Easy Balance with Nutraban? I'm not a fan of this stuff, honestly. Let your tank cycle naturally. Do the necessary water changes. Adding too many artificial chemicals can prove detrimental. You could end up with a bio-overload. Nutraban is supposed to help maintain the bacteria and encourage more to form, all that. I prefer the old fashioned way.
If you are on city water, then most likely, you either have chlorine or chloramines in it. Chlorine will evaporate out naturally but chloramines won't. You can get this info from your local public works or sometimes even online. If you have a well, then you might have trace elements in your water that could be harmful to axolotls (metals in particular). Some don't use dechlorinators at all. Personally, I do. I saw my water report! It was scary...so I use Aquasafe.
I don't think your cycle has started yet if you've only had water in for a week. Thanks for the params, ammonia is another you will need to track if you don't already. Without the artificial stuff, you will need an ammonia source to get your cycle going - as you probably know. Need cycling help, just ask... Hope this helps!
