Stingray

B. lata can be ruled out here as there is not a line of short dermal spines running along the rear body to the base of the tail. I would usually ID T. akajei from the yellow to reddish colouration on the underside, but the blue lighting again makes it difficult to judge colour - I wouldn't rule out T. akajei as a possibility. Do you have an approximate idea of the size of the animal? T. akajei is a relatively small species so size can be useful. As for B. walga and M. gerrardi, I am not familiar with those species so I can't provide any pointers that would support or rule them out as possibilities.

@DaLilFishie I watched a lot of footage so I don't recall this animals size, but there defenitely are smaller sized stingrays in that tank.