A former Northern Territory youth prison guard has admitted to jokingly asking detainees to perform oral sex on him, urging a child to eat faeces and filming a boy urinating.

Appearing before the juvenile justice royal commission, former Don Dale Detention Centre Youth justice officer Conan Zamolo said he was "just mucking around" when he dared a child to "eat shit" and posted the footage on social media app Snapchat in 2014.

"It's just the kids goofing around. Something to pass the day," Mr Zamolo told the inquiry's Darwin hearing.

"I can see now it was inappropriate."