Not the best combo as discus likes higher temp and properly raised clowns are much more aggressive feeders. They also like stronger currents than discus. Rainbow fish is nice...earth eaters work but you still want a mid level to top level fish so your tank won't be empty looking.
Discus do great with them! My friend had a 175 densly planted bowfront with many discus, many clown loaches, cardinals, angels, rainbows and other random fish! BEST TANK EVER! Just Have To Get The Right Temp For Both! (he had like 20 years of fish keeping experiance lol!)
I've seen the discus and clown loach combo a lot around this area and I seems to work. My LFS has a display tank full of discus and clown loaches also a school if roseline sharks. It's
Completely planet with corydoras and Chinese algae eaters in the bottom along with a couple upside down cats. Here's a pic. You cant see the clown loaches and algae eaters but
Believe me they are there lol