Fermentation Temp efficiency - water or air?

New to posting here, busy on other forum, frequent reader, old brewer.

Okay, I'm thinking about rebuilding my fermentation chamber - currently it's a two cooler system, Johnson controlling the ice and water on one side, carboy and circulating pump on the other. I'm tired of remembering to swap milk-jugs: it's time to move up.

I've read/seen several beautiful projects, most moving air, some cooling with water.

I may as well use the cooling power already present in my kegerator, so I'll park this next to it and pump glycol or water between the two, but should I drop the coolant lines in a water bath or have a fan blowing across them?

I love the dorm-refrigerator set ups, but to me there's no point in spending more on electricity than a fountain pump (and maybe a fan) to achieve my objective.
Any engineer-types out there that want to weigh in on this?

I guess the first consideration is, do you have room to spare in the kegerator for a keg of water or glycol? You'll want enough to maintain it's cold temps when it gets pumped. If not, moving air only may be a better bet.

I am by no means an engineer, but my take would be to use two radiators, one in the fermentation chamber, the other in the kegerator. Once you have it filled, the whole system is sealed, no accidental sloshing of the glycol. One of the engineer types might chime in though concerning the need for a resevoir to address any expansion. If that is the case, you could use one of those nicely finished resevoirs that the overclocking folks use for their liquid cooled computers.

Here is a link to a guy who did a similar setup but went with the water bath approach: The Northern Brewer Homebrew Forum • View topic - Fermentation Chiller (Pic's Included) I feel the water bath takes up a lot of fridge real estate though, another reason for the two radiator sealed system. you could mount the radiator almost flat (leave a small gap for airflow) against the inside wall of the kegerator

Did you ever do this? Wondering what you went with. I am about to build a kegerator out of a freezer, and want to also control fermentation temp. This is pretty much the idea I was toying with. Don't have room for a permanent second fridge, but was thinking about going the water bath in the cooler route and pumping glycol through a closed loop in the water bath to maintain temp. I was thinking a water bath would be more temperature stable than just air.