Frank actually brings up a really good point. One that I forgot about until now. I learned this from a biologist many years ago and it might apply in this situation as well.
In relation to Ice fishing. People often wonder why the fish (crappies and blue gills) tend to feed "down" in the morning and "up" in the evening. The reason that was explained is because: as the sun comes up, the plankton and zoo plankton will go down in the water column due to the fact that they do not need to seek out the light as it exists throughout the column. In the evening, as the light begins to fade, the plankton and zoo plankton must rise in the column in order to chase the light. As a result, the fish will also rise with it. This might explain why fish react differently on cloudy days. This also explains why crappies (at times) will hit during the middle of the day in the middle of the water column. This is because there is less plankton in that area and the bait you present might be the only thing to eat at that time of day. This also explains why fishing with a submerged light or a lantern on the ice works so well. It will concentrate the plankton towards the light for that "after dark" bite.
Often times, especially when ice fishing, many people miss where the crappies are at because their fish finder is submerged too deep. In March, it is not uncommon to catch the fish within an inch or two of the bottom of the ice. A clear float puts your bait in the zone without spooking the fish. It also keeps you away from the area and allows you to cast towards them. I love the clear floats because they add weight and allow you to cast a smaller bait (or jig) much further than with nothing at all. Many times, I utilize a gold Aberdeen hook without any weight. I allow the minnow to free swim. A casting weight of some kind is essential to get that bait into the zone.