After discovering very high nitrates in my well water (95 acre farmers field across the road), I sought ways to obtain nitrate free water for water changes.
One of the things I came across was API's Tap Water Filter that produces deionized (DI) water. It removes all minerals and nitrates as well, so the water needs to be adjusted for minerals and pH. This was okay, but I discovered that I could only get about 50g-60g per $25 filter cartridge.
Also, in my quest for lower tank nitrates, I had used both Fluval Lab Series Nitrate Remover as well as API's Nitra-Zorb. These are pretty effective and can be regenerated with regular non-iodized table salt.
I wondered, what if I emptied a spent filter cartridge and filled it with API Nitra-Zorb. I contacted API Tech Support and communicated with Nathan Fekula who told me they had never tested the product in this way.
I went ahead and filled a cartridge with Nitra-Zorb and filtered water. So far I am very encouraged. I was able to produce 95g of water before there were detectable nitrates in the output. I regenerated the cartridge with salt water and I'm beginning another cycle. I don't know yet how many cycles I will get and if the gallons produced will diminish with each cycle.
I will document here as the experiment progresses.