The Aquarium Pharmaceuticals filter works well, but depending on where you live and what the quality of the water and pipes are, you will get varying amounts of water before the filter needs replaced. I clocked the last one that I used at 22 gallons before it needed changed. I am currently buying distilled until my RO unit comes, hoping that the results aren't the same.
No one in this area seems to sell RO water. All of the places and people that I have asked shake their heads and say nope. If anyone in South W. PA knows of a place that sells it, please let me know. Maybe that's just one of the curses of living in an area that has an abundance of a freshwater supply.