Thought about this because of the cylindrospermopsin and microcystin advisory for the Salem Oregon water thread Salem OR- Water advisory issued. What is it, how do you test for it and are there kits for testing or field tests you can perform should SHTF, and you need to collect drinking water. Saxitoxin, Microcystin, Cylindrospermopsin & Bravetoxin Test Kits | Algal Toxins It seems, from what I have been able to find online, that testing for these hepatotoxins is performed in a laboratory environment. I have found a company that produces a test strip that can be read with the naked eye, but they recommend using their digital reader and that to me rings of $$$$$ and I could not find anywhere they were sold. I did read where treating the water with powdered activated carbon can work but to my thinking you would be doing this in the blind, not knowing the concentrations before or after treatment. The blue green algae can live in lakes, ponds and streams so, to my thinking, just not collecting drinking water from a lake or stream would be risky, especially of algae are visually detected. More here Algal bloom - Wikipedia I'm thinking, finding water that isn't going to kill you in a SHTF situation may be more difficult than people believe. And boiling the water doesn't rid it of the toxin, it concentrates it.