Feeding peas is a good answer when your fish are constipated from eating fish flakes exclusively, or for other food-related problems. I feed my fish peas about once a week to curtail any problems. I just use frozen peas, put them in a little hand strainer, run them under hot water until they're completely thawed, then I just press them through the strainer to deshell them and get them into pieces small enough for them to eat. Only problem is it fouls the water for a few minutes but it does clear up quickly.
If your fish is still alive he might come out of shock. But it's still the chlorine that I worry about. It should be store open time across the pond by now. So if you're going to get dechlorinator, get the good stuff like Seachem Prime and dose at least as much as the bottle recommends. You can overdose a little with no harm, just don't put too little in the water.
Please keep us posted.
And frankly, a fish in that condition likely won't be eating anything.