I bought a Refurb 90g unit last year when I got back into reefing and ordered a new set of filters last week suspecting it was attributing to my algae growth that I had been fighting. When I took off the sediment and carbon filters, they weren't the slightest bit dirty or wet. They looked like they were just installed. I looked a little closer to the plumbing and there is no way water has been getting to those. It looks like my lines go straight from RO membrane to DI cartridge! When I received the unit originally, one of the fittings was broken but there was no hose plumbed in so I just removed it without thinking anything of it. Now, I've had a solid TDS thus far but I can't help but think that those 2 filters play an important role for the life of my RO and DI filters. I'm going to shoot you guys a call and hopefully we can figure this out.