I was planning on buying some Polar Pure and saw that the label says it may no be effective against cryptosporidium.<br><br> After reading various posts on this site and learning terms such as reverse osmosis and adsorption, I'm wondering if I could use the Polar Pure first on the water and then run it through a homemade filter of activated charcoal.<br><br>Any ideas? Or am I getting overly concerned about the crypto issue?<br><br>Thanks!