Get the smallest you can find. Remora, bamboo, cat shark. They need at least 150 gallon aquariums IMO. Some people will say you will need bigger, but it is up to you. The bigger the tank the better though. They will eat just about anything including fish that will fit into their mouths and they produce a heavy bio load. They are hardy though. Do lots and lots of research before you just jump in. The tank should be bare except for some deco's or a couple pieces of lr and have good filtration also.