I’d just take the tank and clean it out and store it - in the barn, under the house, somewhere until you want fish again. I’ve found over the past thirty years I do and then don’t on a regular basis. After giving away everything and then replacing it a couple of years later at quite an expense, I finally just store my tanks in the shed until I’m in the mood again.
Well, we’ve decided, at least for this year, to do the tadpoles. I called and you can get tadpoles for free from the pond supply store :~) I think it’d be fun to watch them grow up and hop away, and then this fall I’ll put it away before it freezes, and if the mood strikes me I’ll do the same next summer.