At a cross roads

I had first bought one off of Ebay, but it leaked, and then i could not get the cartrige refills. Investing in something so important is critical. Personally, I would skip the ebay ones and go with a sponsor here for a quality unit.
I would also invest in a hand TDS meter. They are about 20 bucks at MarineDepot. I use it to double check the system is working correctly.

 

I only feed flakes once a day. And I feed the corals maybe once every other week.

 

Absolutely agree with JBL! I cut back feedings; washed frozen foods; stopped phyto; cut back photoperiod; CUC from John; lawnmower blenny; scopas tang; ran manual GFO; changed light bulbs.....everything except check TDS of source water!! So, I bought a MaxCap SpectraPure RO/DI. It comes with 2 inline TDS meters...very nice! I rigged the old machine up for just drinking water & gave it to my Mom so she doesn't have to cart drinking water.
Also, I even built an Algae Turf Scrubber for active transport of nutrients. Look into this. It works!!!

Good Luck.

 

I have the exact same RO/DI unit as the one in your first link ... ordered from the same Ebay vendor.
I can't complain about it one bit.
Easy to install-easy to operate-works like it should.
Had mine for about 7 months now....probably getting time to change the filters.