well clown fish are odd so if he acts odd dont be alarmed, what type of clown is it, can you giv me tank stats, sometimes True percula clown fish will not eat, my true perc didnt eat for 7 full days, i worried but just kept feeding him and eventually he came around after he grew hungry, they can be difficult to feed if they are form the ocean, but just keep trying, he coudl be sick but i doubt it, but the type can only determine that, most other clown fish dont usually have problems eating, what are you feeding him, otu of flakes, bryne shrim is usually the best, they wont eat any omnivore food hopefully you arent trying to feed him that lol
good luck.
o also, they can b picky lil buggers so if they dnt eat and you get too worried keep trying different types of food, it might only want live-frozen food, if so you might get frozen bryne shrimp, and ween him into flakes... but if im reading this correctly you say your gettign afish in a few days? you need to wait a month to add each fish at least! if you add too many fish at once it will easily overwhelm your tank and any number of things could happen.
1-2 is fine but any more and thats pushing it