DI resin cartridge order

[Aframereef]

I noticed in your video
(RODI Water Filtration Upgraded with BRS Pro Series DI Resin - BRStv)
stated you must install the cartridge in an exact order or the system will not work. Can you explain why this is because my system has always been Anion, Cation, mixed. You are stating you must run Cation, Anion, Mixed. Just looking for reasoning as to why you want the Cation before the Antion. Thank you

 

[Bulk Reef Supply]

The reason we want the Cation first is because the Cation resin will exchange all of the positively charged contaminants with a hydrogen. This in turn creates a variety of acids with a very strong electrical charge. This allows the Anion resin in the second canister to better remove those contaminants. Essentially what you're left with after the water passes through both the Cation and Anion resin is Hydrogen (H) and Hydroxide (OH) which combine to create H2O. The third mixed bed canister is more of a final polish for anything that may have made it through the first two single bed cartridges.