You cannot keep any kuhli loaches in a 5-gallon tank. Even though kuhli loaches are small, a 5-gallon tank is too small for them.
In fact, very few fish can tolerate living in such a small tank. A single kuhli loach needs at least 15 gallons of water to thrive, and for every additional kuhli loach, you need to add at least 5 gallons of extra space.
You should get a 25- or 30-gallon tank to keep at least three kuhli loaches. You need a larger tank because kuhli loaches prefer living in small groups. Even though they’re not schooling fish, they feel safer and more comfortable with friends.