Like I said otto's dont do so well in a new set up, they need a mature tank with plenty of algae, for some reason they arent keen on algae wafers to begin with and normally starve to death in a new tank. Also Otto's are very delicate when it comes to water conditions too.
khuli loach would be nice they get to the same size as the sumo loach and its good that they are available from your LFS the problem is that they like to be kept in grps. Im not sure you have the space for those when you dont think you have enough space for cory's? Also they like a soft substrate too because they are burrowers.
Some info if your interested -