Sorry in advance but this is probably going to be a bit of a negative post
First off, need to be sure -
is this a Red Finned Shark - Leptobarbus rubripinna?
Massive shark, no way suited for most home aquariums, definitely not for a 55 Gal tank......
Grows to 80 to 100 cm
or is it a Red Tailed Black Shark - Epalzeorhynchos bicolor?
Should be ok in a 55 US Gal tank but thats pretty much minimum size really IMO
Grows to 10 to 12.5 cm
Not very good in a community tank though, so need to be careful choosing tanks mates for this one!
Both are very different species, so be sure when you type species, so you know which fish you have in your tank.
That will avoid confusion in future for you and for us.
Angels .....5 of them, thats your tank pretty crowded and thats without the shark, gouramis, kribs and tetras............as long as your tank is over 55 cm in height, might be ok but.........
Keep an eye on your angels, they may start getting aggressive due to territoriality within each each other especially when they start to pair up....
And to answer your original post, my money is on the angels eating the tetra.....
Shark a close second.