I ran the nano for prob a yr or so. Constant adjustment. Like senji said. Its internal and the water level causes a big role.
Get the larger one imo as long as it fits and is in budget too. $
Skims well and quiet.
I ran the nano for about a year also. Constant adjustment even with my ATO. Also I could depend on the pump getting clogged up every time I blew my rock clean with a turkey baster. Personally I found it to be a major PITA of a skimmer
Thanks guys. I saw the small version working in a little 30ish cube(which is what i have) in southcenter over the weekend. "Looked" cute for a intank skimmer, seemed to produce decent foam and work, and was no more of an eye sore than an overflow setup. Sadly when looking for an intank skimmer, "efficiency" is not at the top of my list, as so much as #1 not airstone/wood block driven, and #2 looks good-ish.