I bought some a couple weeks ago not knowing it was a one time unit. The issue was I am running a Fluval G3 and that bag would not fit in the basket. So I decided to add a couple spoon fulls into my basket along with some basic carbon and an ammonia mixture. I could however probably fit the bag in the hob Im using to run purigen.I am planning on getting a Ro Di unit soon im still no sure where to get one, should I trust a store bought one or strictly offline.