There are a couple of things that come to mind when I read this. One is the obvious point of not dumping your fish into natural waterways or unnatural ones that connect to natural ones. If the owner of a closed artificial pond gives you permission and the fish can survive in that environment then fine, that’s just fishkeeping, but if there’s any chance that a fish can end up in rivers, lakes, or oceans, don’t.
The second thing, and the real reason for writing this, is to point out just how large these fish get. People don’t seem to understand that the little fish they keep in a bowl (heaven forbid) will grow very large when kept in good health and the right tank. Goldfish don’t belong in bowls. For long term success they need the size of tank often associated with marine species. I recommend 45 gallon or above for keeping them for decades. Yes, decades, because that’s how long many goldfish species can live. Don’t be fooled into thinking these are good starter fish, easy to keep, or that they can be in a bowl.
In Australia, goldfish are weighing up to four pounds and disrupting native species.
Source: If you dump your pet goldfish into a lake, it will grow into an enormous pest – The Washington Post