Freshwater fish may only be placed within freshwater fish tanks. If you aquarium contains freshwater this wolf fish would fit in perfectly. However, if this tank is filled with salt water you will succeed in killing it.
Freshwater fish transport salt into the body through the gills, while saltwater fish do the opposite. My guess is that your freshwater fish would die of salt poisoning.
It is possible considering u have a large enough tank 55+. Provided u give the other fish plenty of hiding spots n keep the wolf WELL fed!! The wolf is mainly a night feeder, drop a few feeders in before you cut the light for the night n your good.