As President of the Wise Colin’s Fish Hall of Fame (and a fish myself) I say lay off zebra fish! They are confused creatures who think they are striped horses and spend all day neighing. Unable to speak for themselves except for a whinny, I will speak for them.
Not only are you (homo sapiens) eating the fish of the world to extinction, now you’re wanting to play with their hearts on the way. The poor zebra fish – just because it is a little transparent (hey, who isn’t?) you think it’s OK to fiddle with their hearts. Listen humans, you’ve got your own hearts to play with! And I’m sure you could arrange for a doctor/window glazier to put in a glass panel in your front, if you wanted to look at your own heart.