How about a non linear idea to help solve your design problem. Using the pond water and fish together to create not only a fish crop but also a produce crop at the same time? Aquapoincly(sp?)grown lettuce or vegetables that you then consume, and/or trade. IMHO, outdoor Aquaponics has a great potential for pond owners looking to self sustain.
Fish waste and lettuce go together like peanut butter and jelly
