Legal question:Selling house with built in tank, are fish pets?

[Aquattro]

Ya, I wouldn't say cancel it as a first option, but honestly, this is dumb. What are we talking, half million dollar+ house? And they want to argue over some fish that they don't know a damn thing about?
If they insist, buy an undulated trigger and toss that in. Dirt cheap fish that will give them more grief than they could imagine Or add some guppies.