Many water gardens don't require a pump to keep fish alive. It depends on pond size, number and size of fish and how much you feed the fish. Measuring ammonia is how you know you have too many fish or are feeding too much. Without a pump your only option at that point would be water changes to lower ammonia. Same deal as keeping fish in a tank.

A solar pump wouldn't be too big a help. O2 levels drop at night when the pump would be most needed.

If you keep the pond reasonably small-medium w/ not a ton of fish, you can get a smaller pump that doesnt use a lot of electricity, mine is the cost of a 70 watt light bulb. That netting plan sounds totally unnecessary and may injure the fish if they are all tossed together like a big fish salad. What zone are you - if its that cold that it freezes just wait till the end of November and they are semi dormant, drain some/or most of the water out and just pick them out one by one with a fish net. Because they get so sluggish as it gets colder you can practically pick them up with your hands if its cold enough. Mine go to sleep under the leaves lined up in a row like sardines - its very cute. Not sure why, not like they have any body heat to share with each other!