do to the small size i would go with tetras the smaller ones and kille fish but if he wanted something a little different and interesting he could go with dwarf puffers there only about an inch long and there fresh water so thats makes it easyer also dwarf gourami's would work
I would suggest at least 2 more kuhlis cuz they enjoy being in groups.
And then After that then get a couple Dwarf Frogs they are the cutest things ever!
I've seemed to notice most your posts pertain to "my friend"... If you are asking for yourself dont be embarrased, just ask! But if its truely your friend then sorry, keep on asking.
5 gallons can be hard to work with. you'd probubly want to get more kulhi's and perhaps 1 beta, 2-3 frogs, or some shrimp. i would avoid dwarf puffers they often nip the fins of othere fish, plus their picky when it comes to food.
IMO Kulhi Loaches are on the tight side for a 5g tank. They need a 10g because of the groups they need to be in. I would return it, and go with one betta and one or two ADFs.
Tiger barbs would eb a horrible choice for that tank. Maybe you could still talk him into a few cherry barbs instead? Tigers can get close to 3 inches longa nd super aggressive. Not they will amount to much in a 5 gallon tank. And since it probably isn't cycled I doubt they will survive long anyway. Sorry for your friend.