Review on Enhance Water Quality with iSpring FD15 DeIonization Filter for Aquariums by Nicolai Goler

I used this FD15 DI filter as the 6th stage of my RO100 5 stage system (also from iSpring). It produces RODI water with GPD as advertised and at 0ppm TDS. It would produce over 100 gallons of RODI water within 3 weeks. I've started noticing a slight increase in TDS in recent production of RODI water. These filters should last 6 months or 1500 gallons before needing replacement. I contacted iSpring customer service and spoke to Nick about the faulty filter. Nick asked for photos and details of the order, which I promptly did. He contacted me the next business day and ordered a replacement which helped customer satisfaction. It looked like a good filter and I will definitely use and recommend it