 Bottom-dwelling detritivorous fish can be responsible for turbid waters, because they stir the mud in search of food.Piscivorous fish contribute to turbidity by eating plant-eating (planktonivorous) fish, thus increasing the amount of algae (see aquatic trophic cascade).The light depth or transparency is measured by using a "Secchi disk", a 20-cm (8 in) disk with alternating white and black quadrants.