I am suprised there are guys that actually use fireline on the ice. Man is that stuff tough to deal with, holds water, freezes up. Go with a Flourocarbon and you will be very happy and will catch more fish
On rattle reels we use 8lb vanish and rods we use 6lb vanish. I have really come to like this line for all around use in the winter. Also it comes in bigger spools, between all of us we pick up a 5000 yard spool and that is enuff to do 15 rods and 15-18 rattle reels with some to spare for tip ups and string weeds..