I have the 4-stage Basic Reverse Osmosis Revolution Water Purification System, 75/100 GPD membrane - $90. it came with the faucet adaptor. I have a 29 gal tank
I use two 5 gal water containers I got from my LFS to make 10 gals at a time, 5f or the water change and 5 for top off as needed. Takes about 90 minutes to make 5 gals.
I hook it up to the faucet, make the water, and then store it away until the next batch.
If I fall behind, I drop off an empty at my LFS and pick up a 5 gal container full of their rodi for under $5.
I have never tested the TDS in my rodi, and suspect there my be more TDS than what my LFS sells. Nothing alarming, but I do notice the cyano takes longer to reappear with the LFS water. Just a hunch, but nothing that has me wanting to upgrade the unit. I knew I wasn't buying a high end unit and as far as my needs go, it get the job done.