No offense pinnky, but all of your tanks are overstocked or will be very soon.
Pacu need several hundred gallons. Aros need a big tank, too because they get over 3 feet. As for the Blue catfish, they are basically the temperate version of the RTC. They get over 100 pounds, grow very fast, and are extremly predatory. If I were you, I would seriously rethink your fish choice, especially if a 55 is as big as you can go.