The value of the Blur radius is zero
Then no shadow will appear.
????????????????????????????????????????????????????????????
Well supposing that you want all fish gone -
The answer would be 8
56 (divided) 7 = 8
Day 1 - 48
Day 2 - 40
Day 3 - 32
Day 4 - 24
Day 5 - 16
Day 6 - 8
Day 7 - 0
Hope this was what you were looking for :)