Aquaculturists fill ponds with wells all the time. In fact wells are prefered over watershed water as it has less risk for contamination and other unwanted items including silt.

I have a 4 inch well at 88 feet with a 45 gpm pump on it that I use 24/7 in summer to keep my trout pond cool and flushed. Right now I am using it to fill two new ponds. Ponds are quite small at about 100,000 gallons, 85 by 45 feet and 7 to 8 feet deep (for intensive aquaculture purposes) and it takes about two days to fill them with this pump. I also aerate my well water by dropping it through five gallons buckets filled with plastic media before channeling it via knife gate valves to various ponds.

Cost to run the well on 220 power 24/7 per month is about $100.00. I guess it depends on what you consider expensive.

One more thing -- make sure you have an aquifer that can handle the pumping. Some can't. My aquifer is about 40 feet thick and goes on for miles. I may even have another aquifer under this one.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.