Khuli! I have a pair that crack me up constantly. Always swimming in giant loops and using my bubble curtain as their personal roller coaster. (they even convinced some juvenile platys to try it too)
But Dojos are the best. All 5 of mine are hand tamed hams that I wouldn't trade for anything.
I have 10 Kuhli's in my 20 gal with 3 Serpae tetra, A Dojo loach, and (feeder) brine shrimp. They are awesome to watch, especially at night they are really active.
I also have 6 Clown Loaches living with 5 Pictus-Catfish in another (much larger) aquarium - They too are awesome to watch.
If I had to choose between keeping the Kuhli's or Clowns - I'd say CLOWNS. They are hilarious. But don't get just one. Upgrade from that 30 gal and get at least 4 more CL's.