do goldfish have hearts!?!

so this morning we had to say good bye to goldfish number 9, we have stopped naming them, every time we give one a name it dies, so we have just started to number them! I am not sure if goldfish arent as strong as they were when I was a kid or if in the middle of the night my daughters are poisoning them with jelly beans and bubble gum, both thoughts highly possible! (LOL) but I do remember I had a goldfishthat I swear had 9 lives, our cat who was the spawn of satan herself, had to knock the tank over at least four times, she would flick the goldfish out of the bowl, which as funny as that may sound was traumatic to see, I mean she was going to get this fish anyway possible and no matter how many times we thought that fish was near dead we would put it back in the bowl and it would be as if nothing happened!
anyway so as we wake up to find fish number 9 floating, and not the good kind of float; my 6 year old whose concept of death revolves around Micheal Jackson, seriously when he died she told everyone at school that he died because his heart stopped singing, so now anytime she hears about death it's because people's heart stopped doing something for whatever reason, everything from their heart stopped laughing to their heart stopped playing basketball. so today she asked did the goldfish die because it's heart stopped swimming and her sister interrupted and said goldfish dont have hearts and that the goldfish died cause it drowned, which was pretty hilarious, but then I thought does a goldfish have a heart!?! silly i know to even think of that but not all living things have hearts, right!?! plants don't and they grow and die, jellyfish dont have hearts, living organisms dont have hearts, so do goldfish!?! I googled it and they do! (LOL)