Tekashi 6ix9ine's stay at Brooklyn's notorious Metropolitan Detention Center wasn't long.

And it wasn't pleasant. 

According to TMZ, 6ix9ine got gangsta checked right when he arrived at the facility.

We're told Tekashi, an alleged member of the 9 Trey Gangsta Bloods, was confronted by inmates affiliated with the Crips who were in the intake area as he arrived. That's when one inmate 'G Checked' him -- meaning stepped up to him to see if he's a real gangsta or just a wannabe.

We're told the Crip told Tekashi he better understand who's in charge -- and the only thing that saved him from a beatdown was the fact prison staffers quickly intervened.

6ix9ine's lawyer Lance Lazzaro acknowledged TMZ's reporting.

"[6ix9ine] was being threatened in jail. However, he was not scared nor did he request being removed. The [Bureau of Prisons], acting upon these threats, removed him to a different facility to eliminate the threat," Lazzaro said.

6ix9ine was quickly moved to a jail often used to house government witnesses. TMZ's sources say he specifically requested a jail without Crips or Bloods.

Members of the 9 Trey Bloods, 6ix9ine former business associates, were caught on wiretaps threatening to stalk and "super violate" 6ix9ine for firing and disrespecting them. 

So you can see why the rainbow-haired rapper wanted nothing to do with Crips or Bloods.