The Secchi Stick is a simple analytical device to determine optical density of a liquid. The depth at which the disk is no longer visible is taken as a measure of the transparency of the water. This measure is known as the Secchi depth and is related to water turbidity. We have a video on it's operation on youtube.

New to this? Our guide explains how to use it to track your culture, and how a two dollar stick does the same job as a three thousand dollar spectrophotometer.

PLOT: Nannochloropsis: Dry Weight and Cell count as a Function of Secchi Stick Depth.

Calibration charts: Chlorella and Spirulina.