About the filtration, I was going to do one of three things.
1. Buy a tetramin 1000 gallon pond filter for $79 at Kmart. If it doesn't come with a pump, I will either purchase a new one or hook the pool filter up to it so that it can pump mechanically cleaned water into the biological filtration system which will be on a raised level, letting gravity take the water back into the pond/pool.
2. Build 2 bio filters with buckets, one set higher than the other connected by pvc pipe. Hook up one mechanical filtration pool filter to one end, pumping water into the first bucket, and hook my spare pool filter to the other bucket to pump water through more biological filtration, into the pool.
3. Using plastic drawers, build an easily maintained wet/dry type system.
The pond will not be stocked to capacity. I'm thinking, at the most, 4-5 fish that'll hit 12"+, and around 10-15 dither fish that'll only hit 5-7" max. I am planning to add some plants as well as stuff like daphnia and snails to help keep the algae levels down and help provide food for some of the fish.
Also, I live in California so I will be building a green house around it, just a simple frame covered with that clear plastic tarp stuff, to try to keep the temp up in the pond/pool. In the winter I will be running a small room heater to help with the temp, either that or I'll somehow get my hands on a 300 gallon rubber-made tub that I'll keep in the garage for the cold months.