Question for RO/DI and already existing RainSoft filtration system... what resins needed for already clean water?

[enorl76]

I inherited a 100G+25G sump marine aquarium from my uncle. The RO/DI is a 3 stage: the RO membrane plus 2 DI resin canisters.

It came with that electronic 3 point TDS meter, on the output of the RO membrane, another between the two DI resin holders, and another on the final output. The TDS meter shows about 30ish PPM when flushing, then about 8-10 PPM after flushing, with the 2nd showing 2-3 PPM, and the third point always showing 0 PPM.

I have a 3 year old RainSoft system yanking sediment, chlorine, and various other tap water TDS from our Orlando FL tap water. My question now is, what resins make sure for the RO/DI system?

The current color of the first DI stage is amber, and the second DI stage is dark with some amber on the bottom.

I saw a video from BRS about the various combinations of Anion and Cation and mixed bed, it seems like Anion first then mixed bed second seems to make the most sense.

 

[Reef-junky]

Not sure what your asking. For the DI resin you can run a mixed bed or cation and anion. The order I don’t think would matter. The idea of not running a mixture is if your water has more negative or positive ions in it the other resin will last longer. If you run two mixed bed Di canisters the idea is that you will be able to use up more resin then normal by swapping and refilling the canisters