DO NOT LET IT GO IN YOUR LOCAL WATERWAYS!!!
The world would be better off if you euthanized the thing rather than let it go somewhere it doesn't belong. Heck you could get a couple decent sized fillets out of it. bake it with some butter, lemon & garlic...
Try and give it to an LFS maybe
check with a local fish shop that has special fish, a lot of times they will take the fish and give you credit maybe 40% of what they will sell it for. If they have it there is sure to be someone with a 400 gal tank that would love it.
They won't even take it for free? If not, you still have other choices ~ can you stomach euthanizing it if you knew it was a painless death? Clove oil mixed with vodka before adding to the water will do the trick (take a few swigs of the booze beforehand to ensure it's a painless procedure for all involved ). Clove oil is readily available from a pharmacy or health food store ~ it's a toothache remedy. Here's a page with info on exactly how to do it: How to humanely euthanize a fish. Clove oil is an anesthetic used during surgery. Using it to euthanize the fish is painless ~ he just goes to sleep and never wakes up.
If you still can't do it, mail it to me and I'll do it for you ~ I'll even send you shipping supplies and postage money. I'm serious as a heart attack about that ~ it's how strongly I believe it's a bad idea to dump him in a waterway. Heck, if you're anywhere within a reasonable driving distance of Spicewood (50 miles west of Austin), I'll come pick it up.
I know it's hard to do something like this, but (and I'm honestly not wanting to beat you up about thinking about dumping it ) euthanizing it if you can't find another home really is the best thing to do, by far. Have you seen those stories on the news about those giant fish in the Mississippi River jumping up and into a boat and almost knocking people out? Those are Cyprinidae, same family as your fish. Something to think about.
Let me know if you want to mail it to me or want me to pick it up. I really am serious about that.
I certainly agree with not introducing the fish into the natural waters.
As for the dinner plate, joking aside, is it a good idea considering the amount of fertilizers we add to a small closed environment such as our planted tanks, and not knowing if any medication has been used in the past?