Goldfish possess genetic traits that allow them to swell up to four pounds—the size of a Chihuahua. Experts say that's why ...

But in your home tank, there's no bacteria to be found. You have to introduce it, and that's where a lot of goldfish owners slip up because you can't just buy a fish the same day you get your tank.

the USFWS also recommends returning it to a pet store or donating it to a local aquarium or rescue group. The agency also noted that while it’s legal to use goldfish as live bait in some states ...