The hole: cover or no cover?

[BrianF]

I have some round style ht tipups. They cover the hole mainly to prevent them freezing over but also block out a good deal of light that could shine down the hole. Question though: is the light shining through the hole an attractant or a deterrent to rainbows in shallow water?

Like to hear some opinions on this. I know I have mine based on my use of them vs. other tipups.

[NHfisherman]

I dont think the light bothers them much....I watched one eat my salmon egg today and saw a few more through a gap in the ice next to a tree, I think they cruise in shallow and the light naturally varies with ice thickness,  though i do think they bite better on an overcast day.