How can I measure algae without specialized equipment?

Question

My friend and I are struggling with our environmental studies project. We have one jar containing pond water with phosphate in it. How can we measure the amount of algae without a microscope or a spectrophotometer? How can we estimate the amount of algae?

Answer 1

If you prevent the water in the jar from  evaporating (keeping the filling level constant) the gain of weight could be a measure of algae growth.