I know a retired guide who used to keep smelts in a dug well. He had a wholesaler's license which let him keep more than 2 quarts. This guy didn't sell bait. He used it to take clients trolling. I remember him keeping his smelts alive in that well until July and August, long after every bait dealer was out of live smelts. He did run an aerator pump and use Better-Bait or Finer-Shiner water conditioner. Not saying it will work in your well but it's worth trying.