I have a 6.6g which ran initially for 1 year and a half on a HOB (AQ 20). Had phospate and carbon media in it, although I took out the carbon media after about 2 months since I saw no point in using it. Had a 3D printed overflow box over the intake, although other 3D printed surface skimmers are also available (esp for AQ filtes). You can hook up a Fluval one as well.
For circulation I use tiny submersible pumps like the 53gph ones from
https://www.amazon.com/Aquarium-Sub...TF8&qid=1510301030&sr=8-14&keywords=nano+pump
My only inhabitants were snails (Ceriths and Doves) so feeding was scarce, maybe one algae tablet a week or every two weeks. Water changes once a month. Feeding zooplankton and that's about it. Grew some SPS (montis), LPS (euphylia) and lots of softies.
In terms of "tech" this was very much low-tech, the lights are Dennerle Nano Marinus.
I've "sumped" it last month as I'll be a month in holidays (or even more) next year and the guy coming in isn't an aquarist so I have to ensure everything's as simple as possible (with as little room for error as possible as well). Am also considering a nano ATO for it, which I'll probably get the next few weeks.
If you really want the best non-sump filtration which you can get while not feeding excessively and doing weekly maintenance, then an external Eheim filter is your best choice. The "ecco pro" line is really nice, has a small footprint, their silent, easy to maintain and clean and reliable.
If you choose to have actual bio media, during cleaning make sure to rinse them in a bucket of tank water and not running (tap)water. If you choose mechanical (sponges, floss) filtration those can be rinsed under running tapwater.
