I found this skimmer which is advised to be used in your mini notice the red text below.....
Fission Nano-Protein Skimmer
The Fission Nano-Skimmer is the worlds smallest protein skimmer, measuring a mere 6.5" high and 2" in diameter.
Small size fits most nano-aquariums
Patented hang-on submersion design
Includes air injection submersible pump & suction cups
Easily disassembled for cleaning
For tanks up to 30 gallons
Ideal for all nano-reef aquariums,
Powered by an energy efficient air injection pump, the patented Fission skimmer rips bubbles into a vortex foam froth, breaking apart proteins and organics and efficiently removing them from your nano-home. Easy-to-install, this nano-skimmer packs the power of fission into pint sized perfection creating a safe and clear environment. Ideal for use with tanks up to 30 gallons.
Each skimmer includes a 84 gph (320 L/hr) submersible air injection pump, protein skimmer, suction cups for mounting, hanging clip, two connection elbows
and six bubble reducing pads