One Fish... and No More

Well, the fish only lasted for three days.
Two days ago the inexplicably began staying at the bottom of the tank.
Not swimming. Not eating.
Just sitting.
Yesterday I Googled "fish at bottom of tank not moving look sick" and read that they may have been overfed and now have a blockage in their swim bladder, which helps them rise to the surface. Which makes sense when remembering that I woke up to two DARLING children happily informing me that they had already fed the fish that morning. The common recommendation is a diet of peas (yeah, those kind) and a partial water change.
So that's what I did.
And they all died, except the sucker fish.
Now I thought the deaths would be taken hard by the kids, since they loved the fish so much.
But I'd forgotten how... resilient?... my children are.

"Mom! Two of the fish are floating at the top of the tank!"
"Oh honey, I'm sorry. I guess sometimes fish just don't...."
"Can I flush it down the toilet?"
"No I want to!"
"I asked first!!"
"MOOOOM!!!"
"There's two of them! You can each flush a fish!!"

Good grief.