I wouldn't. They need a tank much larger than 50 gallons. Healthy specimens get to be about 8". That wouldn't mix well with a 45G aquarium. If you really wanted one, i would say 60 gallons is your absolute minimum. Plus, they can be a little hard to feed at first, and being stressed by a small tank will only work against you getting it to eat.
Sorry, but i would consider a different fish. Just my opinion though.