I was thinking maybe a pair of brichardi and a pair of lelupi would work. Otherwise you could do a pair of Julidochromis. A 29 is large enough that just about any would be ok. Come to think of it, any of the Neolamprologus would be ok in pairs, like tretacephalus. Tropheus might be a bit active for a tank that short, but its worth a shot. Personally, I would have a pair of Julies, a pair of brichardis (daffodil), and maybe a Synodontis multipunctatus.