What other fish can you put with clown fish?

That depends on how you are keeping your Discus. If they are in a bare "species tank" with no gravel or plants, I would suggest you don't add any other species. If on the other hand you are going the "decorative, planted aquarium" way then I would be suggesting one or two of the "Corydoras" family as bottom dwellers, a shoal of around 12 Tetras (I like "Cardinal tetras" (Cheirodon axelrodi)) to provide action and colour and maybe a few livebearers (guppies?) to provide a bit of interest for the Discus in the form of livefood to hunt occasionally. As a retired Discus breeder, my advice is to look after their water quality, followed by look after their water quality, followed by keep an eye on their water quality. I can not stress this enough. Discus are as tough as nails provided they have perfect water that suits their requirements perfectly. To keep Discus healthy, daily water changes of at least 10% are a neccessity as are water changes of a minimum of 50%weekly.