I've tryed units like that before and honestly they just don't cut it. You'll be disapointed both with the quality and quantity of water it puts out compared with a full ro/di system. We started out buying water and then baught our own unit. Two months later we have a three times larger system and really happy fish. The FDA allows 500 parts per million Total Desolves Solids for human consumption.
The water we take OUT of our tanks during water changes now is at about 350 TDS...
That going in...0