Well, you’ve done the best you and you can’t control every aspect of every outcome so I’d say you found a new home. You have no choice but to take the new owner’s word they will take care of it properly. If the redtail eats his trout or whether or not he actually heats the current pond or gets a new pond for the rtc is not something you can ensure one way or another. 1800 gallons for that rtc would be wonderful. Good job!