Yup, just give your clowns a couple of days to adjust, they'll be fine. My clowns didn't eat much for the first few days I got them... now I got them eating out of a spoon
Try getting your clowns a variety of food. I currently have my clowns eatin krill, mysis shrimp, cyclopeeze, and the same flake food you probably bought. I'm not sure if the variety of food helped, but my clowns have grown quite noticably since I got them.. and they have turned a really nice red color compared to what color they were when I first got them.
My clowns had a problem swimming in my tank for the first bit as well, they got used to that very quickly.. although it did cause them problems at night when they tried to sleep. For the first couple of weeks, I would always find one of my clowns either stuck in my overflow, or sucked into my sump. I ended up putting one (out of two) of my powerheads on the same timer as my lights... ever since then, overflow/sump surfing issues have been reduced to once a month, rather than once every couple of days
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Have fun with your clowns, and like rodsboys said, don't overfeed them, no matter how much they beg
-Richer