Hi, WELCOME TO AA!!

Normally, a fish should not get stuck in the filter intake. It is not like the filter has a ot of current to it. This would lead me to believe that something is wrong with the fish. I am assuming you cycled the tank before putting it in. Was it ever acting normally? Swimming right and eating? If you get a chance, post a pic of your nano and the clown. Let us know how things go...Lando