Tilapia!!!!
Get on the DPI website and check what to do with them.
They are a danger to Australian waters. You're 'sposed to destroy the fish and throw them in the bin.
This quote is straight from the DPI website:
"Tilapia are the most invasive group of fish in the world."
http://www.dpi.qld.gov.au/28_13879.htm
http://www.dpi.qld.gov.au/28_16290.htm
Cheers,
Jimbo
p.s. Drikus- you have Dutch heritage?