Go Small or Go Home

Judging by the ATI 23″ SunPower T5 lighting fixture that hangs over the reef, we can deduce this rimless aquarium measures approximately 24x12x9 inches putting this tank between 10 to 15 US gallons.  An Ecotech Marine Vortech MP10 provides the circulation and a black overflow box or hang-on filter/skimmer is located top right corner.   Beyond that, your guess is as good as ours.