Quit throwing away cartridges and money.  Buy one refillable cartridge and then just buy replacement di resin.  Can also be used for carbon and other granular media.

Smart Reef^TM +DI (Nuclear Grade DI Color Changing Resin)

1.25 lbs of Resin sealed in a mylar bag to prevent prematurely depletion.

+DI resin color changing is obvious to see. It changes from blue to brown. Some other color changing resins just change shades of color and are hard to determine when they are depleted.

Once the color starts to be mostly brown, use a TDS meter to determine when it is time to change.

New	Check and Replace

Dosing:  

Use in a refillable DI canister. 1.25 lbs per canister.