Yeah, RO, while easy to use, has a lot of concerns. Interesting to hear this from an aquaculturist perspective. My home uses RWH, no municipal tap, we don't lose much of any water. Just the stuff for drinking gets pushed through RO and the rest is on a gray water cycle which goes back into the ground or another exit filter(depending on the drain).
Been looking at methods for re-mineralization for a few years. Considered drilling a supplemental well. Using bentonite/pascilite clay now, which winds up costing maybe $1.50 a year for our usage, so that makes the $2-3k to DIY a well correctly seem silly for the intent of gaining the problem everyone seems to be running from, hard water.
We need to get some fish farming, aquaponics, or whatever the term would be, going on the forum. I love reading about people's ventures. I did tilapia in 50 gal tote for less than a year, and it was just too damn time consuming for essentially a junk grade fish.