My home uses well water as the only source of water. I have a sediment filter after the pressure tank and then to a water softener. I bypass the softener to provide 'raw' well water to my aquariums. The problem with my well water is that I have clear iron which once exposed to air tends to leave a reddish color to the toilet, sinks and other household water uses.
I have had no problems using this water for my aquariums, the fish are thriving and most plants do well.
My suggestion is to have your well water tested for the usual contaminants to see if it is suitable for use as drinking water. If it is, I don't see where it would be a problem for use in your aquariums, of course that depends on what species you would be keeping and the pH, GH and KH of your water tests.
Of course if you stopped using the well water as the primary source for your home due to a problem with the well water and switched to city water, further testing might be beneficial.
As far as I am aware, most cities don't permit having both water sources inside the home at the same time due to possible cross contamination to the cities source water so you most likely only would have access to cold well water from the outside faucets. Heating that water for aquarium use would have to be considered also.
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