give him a couple of days. Almost nothing with pet-keeping goes like clockwork.
Even though snakes are 'supposed to" be hungry righ after they shed, it doesn't mean they are, nor does it mean they will be comfortable enough to eat.
Give it Time and privacy.
Could be your snake is not used to feeder fish.
After a few days, If it still hasn't eaten any fish, try a live pinky mouse.
If you have any ponds near the house, a small frog would be JUST the ticket, but that gets to be a real pain. Your best bet is fish right now.
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...and I think to myself, "What a wonderful world."