Darwin, if you search here and in the archives, you'll find lots of info on water filters/purification. See the sticky on "How to Search" at the beginning of the General Discussion section.

For future reference, there's no need to post identical posts in different sections. One is enough! There are probably more posts about water in "Backcountry Health and Safety" than anywhere else.

My favorite water filter, unfortunately no longer available now that ULA has been sold, is the ULA Amigo Pro. Gravity filter, no pumping, 7.5 oz. so lighter than most pump filters. It used the Katadyn Hiker Pro filter and filtered about 1 liter per minute. I suspect that you could make the equivalent using said filter, a high-quality silnylon bag and some plastic hardware and tubing from the aquarium section of the pet store.

I tried the Aquamira Frontier Pro last summer (in conjunction with Katadyn MicroPur tablets) and was very dissatisfied. The filtering rate was about 10 minutes for one liter, not counting the 20 minute waiting time for the tablets. IMHO, 30 minutes for a liter is far too slow! Trying to drink via the bite valve made my jaws ache but didn't quench my thirst. Also, this filter only filters out the protozoa. Since Aquamira doesn't bother to tell us the size of the filter, I question if it even does that. Per the CDC, it takes a 1.0 micron filter to get rid of protozoan cysts. I've seen reports that the Frontier Pro is either 2.0 or 3.0 microns, which makes me doubt that it filters 99% of the protozoa as Aquamira claims.