Okavango Challenge

I will be testing the effects of different types of water (storm runoff, tap water, filtered water, grey water) on plants, and I need to know what’s a good plant that grows fast and that I will be readily able to notice differences in if it is unhealthy, etc.

duckweed (Lemna sp.) and Elodea (also called Anacharis)

You can get both in most pet stores, you get multiple plants of each (a container of small floating plants in the case of duckweed, a grouping of stems for the Elodea) and they’re relatively cheap (either would be less than $5-6)