I reccomend keeping a species tank (only one type of fish) if you are interested in the freshwater barracuda. The only type i know of is the hujeta (Hujeta Characin, Ctenolucius Hujeta, etc, etc. It's all the same stuff.) These grow to be 28 inches long, and most reccomend a tank size of at least 135 gallons. If you would like to take a chance, however, I have also heard that if you start them off in a smaller tank (Your 85-gallon will do fine here) they will stay smaller, at around 10 inches. At this size, you could easily keep two or three in your aquarium.