Well, yes and no. A small snail or some shrimp wouldn't add much to the bioload, however the tank isn't stocked very well unfortunately. The danio and tetra are schooling fish and need at least 6 plus they are pretty active and would appreciate more swim room than a 10 gal
can provide them. The khulis prefer groups as well and a 20 gal
is minimum. Mollys are messy (e.g. have a high bioload); one would probably be ok in a 10 (that's debatable though), two is pushing it and two with other fish is really pushing it. What type of frog? African Dwarf frogs are social and prefer a small group but I'd say you're fully stocked. So unfortunately long-term you'll have some choices to make; either upgrade to at least a 30 gal
to keep the fish you have now and add to the tetra, danio and loach groups (I'd keep the frogs alone in the 10) or think about rehoming some fish.
Also is this a new tank? You might want to read up on cycling if it is:
I just learned about cycling but I already have fish. What now?! - Aquarium Advice
Guide to Starting a Freshwater Aquarium - Aquarium Advice