Been doing a lot of research on water purifiers / dechlorinators etc.

I have found it a total minefield but believe I'm getting close to having the most appropriate purifiers for my water.

But one thing I'm struggling with is ion exchange Water Softener cartridges.

This one in particular:

Water Softening Filter Cartridge FCCST | Aquafilter

Can someone please answer the following:

Are they safe to use on Koi ponds?

Am I correct in assuming the output of the Ion exchange is sodium chloride, i.e salt?

If yes, Is the level of salt produced significant enough that it shouldn't be used on a pond?

Does anyone know what the output salinity is likely to be, and as salt can only be removed via water changes, does this mean the pond salt level will gradually increase over time due to evaporation followed by top ups etc?

Once I've got the full picture I'll create a thread detailing my various findings for non-RO purification, and ultimately whether its worth i at all.