That's undoubtedly overstocked. Even if the filtration can handle all those fish which is quite impressive with all the waste manufactured and food needed, other problems are bound to arise. Territorial issues and space. There's not enough room for each fish to claim it's home in the aquarium and not to mention they're being packed in there like sardines! And the atrocious fact that there are multiple tangs in a 50 gallon makes it even worse. I don't see the justification or success long term of having so many fish in a small aquarium.
“Success is walking from failure to failure with no loss of enthusiasm.”
- Winston Churchill