they need cool water (77 ish), a good current, and are quite nasty ... yarelli is quite active whereas B bagarius is quite sedentary ... both are aggressive tank inhabitants and will ultimately need to be kept on their own.
B yarelli grows very quickly and will get to about 18" in a year or so, B bagarius is slow growing, mine has grown at about 1" every two months ... certainly no quicker .. max size for the former is in excess of 6ft, the latter will only reach about 18"
carl