Here is the deal...having built every little ghetto system in the world, i can say this...I always had water temp problems when I used pump inside res...so,

Here is what I would do. Get a 10 gallon sterilite tub(for your rez)...make that your rez. In your 5g bucket add a boat style 3/4" bulkhead fitting in the side 2" up from bottom of growing bucket(use aquarium sealant to make watertight...attach a 90degree and turn it down through a hole that fits snugly in top of 10 gallon sterilite(this is your drain)....put you pump in the 10 gallon (more water volume=lower water temps) tub, and extend your feeder lines to the top of 5g bucket. It will take some Mods, but I did it and you will be happoer with all your results.

water temps should be 65-70 degrees in your rez for optimum oxygenation...Z says "68 degrees is perfect"

got it? I'll be back...by the way...Nice job with the info "slowthestone"