How can I reduce the amount of hooch my sourdough starter is making?
Hooch formation is a sign of a starving sourdough starter. I've never actually had hooch forming on a regularly fed sourdough mother. So this is the short answer.

I've sometimes spotted something similar to hooch, but it's just a false sign; Twice a day I feed my sourdough starter (it's at room temperature), and I clean my glass jar each feeding. Sometimes a small amount of water is left in the jar, and when I pour in my sourdough it doesn't incorporate the water. This water over time moves on top of the sourdough and looks like hooch, but isn't. This might or might not be the problem. Remember, a room temperature sourdough should be fed twice a day. I don't have much experience with cold-storage sourdough, but once every second day should be good.