I've Seen them , never Built one. I would think 5 gallon might be too small I'd start with 10 gallon min. I'm not an Expert so I would defer to others with more experience.
There is a Guy up in nova scotia who has a DIY site for all things Aquariums.....
Try E-mailing him....he is on Facebook too...
60 gallon(Parrots and Convicts) 55 gallon African Cichlids 5 gallon Betta tank 35 Gallon Hex (Bolivian Rams, Oto cats, Bloodfin Tetra and a shoal of Tiger Barbs) 75 Gallon Oscar Condo. 30 gallon GBRs & Danios