There are 22 species of introduced fish in New Zealand. This is a lot considering that New Zealand has only got 39 species of native fish. Like all introduced species, they have some impact, but some cause more problems than others.
There are many more introduced fish species in New Zealand than those described here.
Aquarium species that have escaped into the wild are of growing concern. Please don't empty your aquarium into your local stream, as your pets can become pests.