I have to a agree a large red arrowana would look spectacular. I would also add some large datnoids and some peacock bass. My peacocks eat pellets along with frozen krill so do my datnoids and my green arrowana
If you are going to put Bala Sharks, why not get some tinfoil barbs or denasoni aka red-lined barbs. Both look sharp and you will have many different types of colorful, schools. Clown loaches are a must and don't forget about rainbow fish!