Is it okay to have Kuhli Loach in a 3 liter tank temporarily?

i think that it would be fine. Just make shur that you have an air supply or filter. heater is not nessasary unless its gonna be outside, in the stic, or basement. room temp is fine. Something that small, be shur to change the water very often, maybe exchange half every week being shur to use dechlorinator. I have a couple of kuhli's my self, very neat fish to watch.