I have a question about DI filter replacement. At what PPM do you guys change the DI filter media? Mine has just started to read 1-2PPM TDS. I am only using it for top off as you all now I have scrubbers so I dont water change. My tanks (all three) usually need about 4-6 gallons per week for Kalk top off. Is 1-2 PPM TDS bad enough to change the DI media?