Heres how to figure volumn needed; load empty reels into tank, fill with water approx. to half way in tank, hold clear plastic or glass over open end, turn tank horizontal while holding sight glass firmly against end of tank, note fluid level in tank. If theres enough liquid to cover all film, then you are finished, if not add more water and check again. When you are comfortable that you have enough, pour liquid into measuring container, and make note of volumn.
Or, look on the bottom of the tank, some makers post vols. required there.