No, these don't appear to capable of producing the water quality that us reefers are looking for. From whats mentioned in the Q/A each filter only lasts for about 20 gal. before the TDS starts to rise, which would get pretty expensive over time.
An RO/DI filter is the only way to go at this time, and will be worth the investment in the long run, both in pure water and in the cost that you may procure fighting algae issues in your tank. Even with a Nano-tank.
i have to agree.. the zerowater filter would work as it would get you a 0 TDS reading,( i think the even come with a TDS meter, one i had did) but the cost of replacing the filter in the long run will cost you more than the investment of an RO/DI. And with a nano the filters and resin should last a bit barring you arent changing water daily lol.