I have the small TH feeder. I fill mine with about 5 gallons, about 20 lbs if I had to guess) about every 1.5 to 2 months.

I don't really notice any moisture in the feeder except (very rarely) one of the viewing windows will leak a bit during extreme weather events. However, I'm more concerned about the heat. My pond is in south Miss. so temps around 95 are not uncommon. I'm to understand that the high temps can make the food turn rancid faster than normal storage temps.

1 ac pond LMB, BG, RES, CC