The formula for you is the same as for two nested
cylinders.
Figure the volume of the larger
first (pi x
radius squared x depth) or 3.14 x 25 x 1.5 = 117.75
cu. ft.
Subtract the inner cylinder (4 x 3.14
x 1.5 = 18.8)
117.75-18.8=98.95
then add back the volume of the deep
cylinder (3.14 x
4 x 3 = 37.68 + 98.95 =136.63 cu. ft.)
Multiply by 7.48 gallons per cu. ft =
1022 gallons.
Remember to add the volume of your filter as well.
