Freshwater tropical aquariums sharks are not from the shark family but are closely related to barbs from the cyprinidae family. They are very popular especially the Red Tailed Black Shark, which I believe almost everyone has treasured one in their fish tank at some time.
The sharks are all bred in Asia, where most are originally from. They are bottom dwelling fish who scavenge for food and will eat just about anything. As usual a balanced diet of flake, sinking pellets and frozen foods keep them in perfect health.
Sharks are quite active and will chase other long fish who share the same areas, so its not a good idea to keep too many in a small aquarium. I would recomend only one in a tank under 90 litres. I would also provide them with plenty of wood or rocks to form their territories. They can then chase each other around but hide away if it all gets too boisterous.
Silver sharks are on of the only sharks that will shoal and can be kept in large groups, but they will grow quite large.
Again the golden rule applies that fish will eat others if they are small enough to fit in their mouths, so no neon sized fish with adult sharks.
Coming from Asia, they will thrive in broad pH range from 6-7.5.