Somehow missed this post but I can respond to your electrical questions. First let me say that there is no problem with running electricity to your pond. I have it ran to my pond.
You need to know how much current your aerator pulls. It should be listed on the motor. It is listed as the FLA (full load amperage)
Run PVC conduit for the wire, from your electrical box at the supply end to the area of the pond where you want an electrical feed. I suggest that you use wire which is rated for wet conditions. Any supply house sells this conduit and wire.
A 14 guage wire can handle 20 amps.
A 12 guage wire can handle 25 amps.
A 10 gauge wire can handle 30 amps.
An 8 guage wire can handle 40 amps.
The distance is no problem. (the electric company runs wiring for miles.) I would maybe upgrade my wiring by one size if I were concerned.
Use weatherproof housings for your plug-ins at the pond. Be sure and use a GFI equipped receptacle for safety. If you want, you can build a little "dog house" to protect your aerator from the weather. Mount the receptacle inside the dog house and all will be OK.
