Rasmussen L, Buhse H E, Groh K
J Protozool. 1975 Feb;22(1):110-1. doi: 10.1111/j.1550-7408.1975.tb00952.x.
Rates of removal of suspended India ink particles from the surrounding medium by 2 ciliates, Tetrahymena pyriformis strain GL and Tetrahymena vorax strain V2S, have been measured. It is evident from the results that the food vacuoles concentrate the suspended particles, clearing a volume of the surrounding suspension fluid 500 times greater than the total volume of food vacuoles made during the same period of time.