I think we are talking about two completely different types of fish in this thread.
Silver shark is a common name for Bala sharks, a.k.a Balantiocheilos melanopterus is a completely freshwater fish, it is a shoaling fish (so needs to be in a group of at least 5-6 indviduals or more to thrive best) that is very active and quite skittish and do best in tanks at least 5ft in length and 2ft in width, although the bigger the better.
Bala sharks can grow to around 12inches+ and are not true sharks, they are just called sharks because of their shape, they belong to the cyprinid family of fish.