What was the class for? Water sanitation/conservation, or...?

I would imagine that water from a reptile tank to have a much higher amount of micro fauna than, say, a mountain stream. (Salmonella and other nasties comes to mind. Blegh!) That said, even a cold, clear alpine stream can harbour giardia, which can only be filtered out with a 1 micron pore size. A coffee filter only sieves out to about 20 microns, so yeah, I'm not surprised that some critters got through.


As for me, I'm a big fan of filtering then boiling. (Potable Aqua works in a short-term pinch, but doesn't kill cryptosporidium and a few other bugs.)