Hello

well... first off i dont mean to be the bad guy, but it has to be said. Your clown loaches will outgrow your tank. You need at least a 55 gallon tank for them.
Whooo enough said

A DG is a very, very colorful fish with lots of personality. I have not kept them, but have talked to members about them and they seem to be very good additions to tropical tanks. Another good fish would be Rainbow Fish. I am not an expert, but i believe there is a specimen that will do well in a 20g tank.
As for the
CAE( chinese algae eater)
i would not get him. I have one, and yes he is cute, yes he keeps my tank clean, but he is VERY agressive. He posessed half of the tank. Not forgetting that they grow rather large. They have been known to suck the slime coat off the fish. Yes, when young they eat algae, but then they realize the slime coat is better. I like to think of them as the sharks from the Freshwater Aquarium. I bought him as an "albino otto"
he looked like one, untill he grew to 4 inches! so i would stay away from CAE's

There is a few otehr bottom dwelling fish similar to the CAE. There is the FLying Fox, The SAE ( Siamese Algae Eater) and a few others i cant remember their names.
best of luck!

tony