They get BIG, and they eat a lot, so I hope those goldfish are feeder fish, otherwise you might want to put them in another tank, or buy a tank divider.
Jau are the meanest catfish I've ever kept, hands down. They grow pretty quick (2-3" a month), get HUGE like 5ft & 100lbs+ and the only tank mates should be considerably larger then them if you want them to stay alive and not be feeders. I know Cliff (Necrocanis) used to have a larger one that was maybe 18" and it chomped a 12" channel catfish in half...the small one I had beat up a marble pim 1.5 times it size and killed it and attacked almost anything that came near it. They are awesome but you need a large pond to house one if you plan on keeping it for any duration of time. Feed heavily to keep tank mates from being on the menu, good current is also a plus for these fish and higher oxygen levels.
Can only back up what AmazonfishMan has already said.
Zungaro Zungaro / Paulicea Lutkeni (old synomn) is potentially a huge fish of over 5 feet in length.
They have the bulkyness to go with it and regulary exceed 100lbs.
They are also particulary aggresive and will harass / kill most tankmates that they are unable to eat.
They require excellent filtration & huge aquaria/ ponds to house sucessfully as they grow.
Almost forget more than one specimen can very rarely be kept together.
I have a few they are awesome be prepared to provide a huge tank or pond. Surprisingly don't know if it's just me but mines don't grow as fast as my rtc. Rtc are more active in my experience. but these guys are meanies and do get huge.
