The Tunze Mini is pretty small.
koralia nano too large?
micro jet lol 1.5in x 1.5 in x 1.5 in 75 gph
mini jet??
Stick a mini jet in the overflow and rig a tube to the display.
Get a mini tunze like $15 tops and they are small but move alot of water for their size. They have adjustable flow rate and are about thse size of a box of floss. I love mine.
http://www.premiumaquatics.com/Merc...oduct_Code=T5024.04&Category_Code=Tunze_pumps
The tunze mini is really small and does move a lot of water for the size but it has suction cups so it doesn't stay on the glass and it seizes up fairly quick. I had one in 12 gal aquapod and it was a real PITA! I would do something like Cindy suggested with the minijet in the overflow.