I got a 1/2 horse chiller chilling 55 gallons, overkill I know but when buying a chiller always go bigger than you THINK you need. I went to buy one at the hydro store and dude tells me you can't bring this item back if it doesn't work for you, meaning there are many many variables that will determine what size chiller you really need. If its just a 5 gallon bucket I've been interested in trying one of those ice probes , they're made for aquariums I think but can be implemented in anything that needs water cooled . Ice probe are peltier coolers , you drill a hole in the container and screw this thing in , theres a cold side and a hot side, the bad news is that you'll have to get rid of a little extra heat in the air since the ice probe uses a heatsink and pc cooling fan it will radiate some heat I'm sure but then thats what exhaust fans are for.