35 gallons is too small for a ghost knife or for clown loaches. And I imagine a ghost knife might eat the khuulies. A better idea would be a bigger school of khuulies; they become a lot more confident in schools of 4-5 and you will see more of them. If you do that, and get the bristlenose, you'll still have room for some top/middle-dwellers.
If you want to see the size clown loaches can get to, check out the thread on Basle zoo- brilliant pictures.