The bala shark (Balantiocheilos melanopterus) comes from southeast Asia. Despite its shark-like appeareance, this species shares a closer genetic affinity with goldfish than true sharks. They can thrive in specific types of community aquariums, with some important caveats in mind.
The biggest issue with bala sharks' compatibility -- and I heartily apologize for the pun -- is their size. Bala sharks are often sold at a young age, when they only measure a few inches in length. But these fish grow quickly. Even large, peaceful fish like bala sharks will eat smaller fish. Their size also necessitates a huge aquarium of at least 200 gallons for them to truly thrive.
Other Bala Sharks
Bala sharks' first tank mates should always be other bala sharks. These fish live in large schools in the wild for protection. Without other members of their species, they feel vulnerable and become stressed. In captivity, you should keep them in groups of at least six. This is part of why they need such a large aquarium. A single bala shark could live in a smaller tank, but stress would leave in prone to illness.
Other than their size, bala sharks make great community fish. You can keep them in "large community" tanks with other large peaceful fish. They get along well with large barbs like tinfoil barbs -- also called silver sharks. Large plecos also make good tank mates, since they get too large for snacking and hang out in the bottom of the tank out of bala sharks' way.
What to Avoid
You have to avoid certain fish for an aquarium with bala sharks. Anything small enough to fit in their mouths has a high risk of becoming a snack. However, despite bala sharks' unusual size, these fish are pushovers. So avoid aggressive fish or fin-nipping fish. Bala sharks can't thrive when other fish pick on them.