In a small saucepan combine ½ cup grapefruit juice, sugar, and peels. Bring mixture to a simmer over medium heat. Simmer for 3-5 minutes until sugar is dissolved and mixture is reduced by some. Remove from heat and remove peels. Let cool completely.In a large pitcher add sugar mixture and remaining grapefruit juice. Add sparkling water.Now for the floats! Add 2 or 3 scoops of ice cream to a glass. Fill the the glass with grapefruit soda.Enjoy!