It looks like zebrina.
One year ago I bought two zebrina 5 and 6 inch long, now they have approx 12 inch (with fins). I have them in 120 gallon aquarium (70*20*20inch).
They eat any fish up to 3,5inch, and kill any fish up to 4,5inch. They usually ignore bigger fish. I lost one 5,5inch Satanoperca few month ago, but I am not sure, if it was due to zebrina attack, or zebrina attacked already dying fish. Other Satanopeca and plecos (6-8inch) are ok.
They eat any food I give them, even pellets for herbivore fish. They are shy, especially they don't like changes in lighting. Whey I used flashlight during nigh, one zebrina jumped from the tank.
If you can, buy more than one zebrina. Mine two zebrina are all time together.
(I know I have small tank for them, but I cant have in mine flat bigger tank and they were on super bargain. Sorry for bad English.)