But it's got 'nanotechnology'!
In other words, the same really small holes every other water purification filter has. What it apparently doesn't have, however, is any way to deal with chemical contaminants (like whatever killed that fish).
Here's a reputable filter from a reputable company, which does as much & more.
FYI, I drank out of a cow pond for a week using nothing more than coffee filters, boiling, & bleach. Good times (to have kool-aid).