HUGE Goldfish! They get really big when they are released into bigger bodies of water. Goldfish grow as big as their environment allows them to. If you keep them in a small tank they will stay small, if you put them in a lake they will get huge! They are an invasive species and cause lots of damage. If you catch one you can’t release it, it’s actually illegal! They get in the water when people release them, using them as bait, or sometimes in rare cases by flushing them down the toilet! Believe