The Rainbow, black and RTB sharks are all solitary species so it is a case of one per tank
Balas, apollo sharks and cigar sharks on the other-hand are shoaling species
Rainbows and RTB sharks require a bare minimum of 50USG, they can become territorial and in tanks any smaller this turns into aggression, tankmates of a similar shape should be avoided as they will most likely be harassed.
Rainbows are generally less territorial than RTB sharks but with any species indivdual fish differ
They can be kept in a tank with relatively peaceful species like neons or guppys provided tank is of adequate size
All other species mentioned above shouldn't be kept in tanks of around 5feet in lenght with a minimum depth of 15inches