Climate control is essential for keeping guns free of rust. As noted, guns can be stored safely at a wide range of temperatures, so long as the humidity is controlled. Not too dry or too moist, and never permit the temperature to drop below the dew point. Things like Goldenrods or low wattage incandescent light bulbs put off just enough heat to keep gun safe relative humidity low enough that moisture can't ever condense onto the metal. I have never heard of a Goldenrod melting, but any electrical device can fail.
I had one of those canisters years ago and ended up throwing it out.
Dessicants can work very well, but naturally, once saturated to their limits, they absorb no more moisture. Things like silica gel or bentonite/clay dessicants don't ever wear out, and can be reactivated by baking them in an oven to drive out the accumulated moisture. The trick is remembering to do so. Calcium chloride is a very effective dessicant, but becomes liquid as it absorbs humidity, and is very corrosive to steel. There is also the risk of getting the atmosphere too dry, to the point that wood may shrink or even crack.
A large bubbling aquarium is not compatible in the vicinity of guns, unless humidity is monitored and controlled. I have had great luck in recent years with wrapping guns with VPCI plastic. I even put VPCI paper in my metal roll around tool boxes to protect the tools in my shop from rusting.
