Welcome Eric .
I would invest in your own TDS meter . 350 -1450 is ok to undrinkable for the range ? I use the HM 3 which is like $20 on amazon or ebay.
I know AZ has hard water but it would help to know and is needed if you end up going to RO and wanting to mix it with your tap IMO.
You could have 6 discus to grow out in the 55 IMO..
Most get small 2 inchers and learn as they grow ..