Interesting thread, Taylor.
I wouldn't recommend an odoe pike. Odoes are EXTREMELY aggressive toward young versions of one of their only predators: African tiger fish. One cannot help but notice how much your 'cudas look like an ATF. A viable alternative would be a Ctenolucius hujeta, the silver pike, or any other fish from Ctenolucidae.
As was previously mentioned, any macropredatory catfish such as a tigriunus would be or would eventually be a serious threat to your silver tooth fish that do their best to look like bait. IF you want to add that wow factor only a tig can add, wait till your 'cudas are at least ten inches. Even with doing this, your time will be limited.
I like the previously mentioned idea of a jaguar catfish, Liosomadoras oncinus. They're beautiful, generally peaceful with a max size comparable to what you can expect from the 'cudas. They are however Auchenipterids, which means they're from the family of catfishes with huge mouths that are notorious for eating anything they can swallow, as proven by the most famous member of its family, the gulper catfish.
I look forward to future updates on these attractive little toothy torpedoes.