Lol sorry I have no idea what kind of fish these are either! I've seen several types but can't remember the names. Is there any that don't grow too big that get on with smaller fish?
Ahh, a problem there! there are no "small" sharks in the hobby, unless you consider 7-8 inches small.
the Red Tailed Black Shark, is about the smallest at between 5-8 inches. it also needs lots of water, usually stated as, 50 ukg+.
the Rainbow/Red Fin Shark, can get up to 9 inches, and has similar tank requirements to the RTBS.
the Black Shark, can grow to 30+ inches and will need 100ukg+
the Bala/Silver Shark, get to 12 or so inches, and again need 100ukg+. they should also be kept in shoals, which takes the water volume up even more.
the Columbian Shark/White tip, Silver Tip, grow to around 14 inches. again needing a tank of about 100ukg. it should also be kept in groups. it is also Brackish when mature, and really suffers if it does not have it.
the Iridescent Shark/Pangasius Catfish, Shark Catfish, can reach over 40 inches. and needs, about 150ukg.
this is not a definitive list, I'm sure i missed some, but it is representative of the "shark" stock out there.