triggeraa, eventually, if not sooner I expect that you'll have some additional difficulties with your barricuda as a diet of freshwater feeders will eventually cause his immune system to break down.....you could purchase filets of ANY kind of saltwater fish at the local supermarket which would be a massive improvement.
Living on the coast in Florida, we occassionally catch juveniles and rear them in our 300 until about 12" to 18" then return them to the sea, and the average growth rate is about 3" per month, the reason I say "additional" problems as yours is way below the norm.(we've probably raised and observed 20 or more over the years)
For anyone wishing to maintain a 'cuda, there is a close relative called a Sennet that often only grows to about 12" to 15" that has the same dentition as their larger relatives.
We've always maintained them in our community aggressive/predator tanks and have no problem except that they are occassionally picked on.....they are predatory but NOT aggressive, except at mealtime and will almost always try to run from a confrontation, much like a freshwater pirana.
I've attached a photo of our last one next to one of our volitans lions, who actually waited underneath the 'cuda and fed on the parts it dropped when it was fed larger prey.......once siezed and held sideways in the jaws, you wath the "cheek" muscles clench and it was cut cleanly in half (the 'cuda would swallow the tail section while the lion snapped up the front)
Surprisingly, one thing we've noticed is that baricuda swallow their prey TAILFIRST when it's large enough to matter, to my knowldge the only pred that does this.