That looks like a good one and it gets pretty good reviews. As far as suggestions go, right this very moment I too am setting up a new 20g system and I'm going to get the Tunze Nano that lists for $99.99. In fact, someone just had one listed for sale on here for $65. I used to only use the Elos ATO but I switched to Tunze years ago and haven't looked back. They've always just worked and whenever I've had any issue, the customer support is great.
The biggest issue with the Nano is that it's controlled by a float switch. The larger Tunze Osmolator is controlled by an optical sensor with a float switch that functions as an emergency kill switch. I prefer and believe that the optical sensors are better and I really like having the float switch as a backup. So why on earth would I go with the Nano? Well, my display tank has the larger one and it's been installed for a long time and the float switch still trips whenever I turn off the return pump for maintenance. I've never cleaned it or done any of the things I really should and it still works.