I disagree with this based on two reasons....shell dwellers would be as far as i go in a 10g. Rams and other dwarfs for a singel fish would be 20g and for a pair 20g is small but 29g would be better.
1) Most shelldwellers will quickly overpopulate the tank.
2) Not all 'shellies' colonize well. Even my multies have disputes in my 55 gal.