The media starts turning purple within a day. It gets used up from one side. You don’t need to replace it until it is all purple. If 2 weeks got you 1/4 purple you are set for it to last roughly 8 weeks total.Yea yea I'll check it out thx. The document though I'll save for if I hit a wall thx or get some free time. I think my co2 media is trash its purple like a quarter of the way down the reactor, sux it's only been 2weeks. Supposed to last 6weeks. It's that 2 little fishies brand stuff cdx ordered some other media today. We'll see if that works