Should I put a heater in my outdoor pond 3x5 ft 24" deep? It will freeze 18" deep. How about feeding them untill it freezes.and after it freezes.

Bud, it depends on whats in the pond - shubunkin and comet can be left the way the pond is right now, while any fancy goldfish would definetelyl need a heater.
I plopped a heater in all my outdoor tubs yesterday, the night temps fell to the mid 30's, days are up to 50 something....brrrrr.........