barracuda are schooling fish yes, bu tthey often can be found as singles(normally only larger ones though), in hte wild
and as for those monsters, the ones in the atlantic and carribean do get as large as the ones from the pacific, i know from personal experience exactly where 3 are(and i do not dive much, in fact only one time) one is over 6 ft long(my wife tried to get a pic of me swimming with him, but she was too far away for the light we had avail, so only a shadow is present in the foto) and teh other 2 are near if not 5 ft, and have seen many over 3 ft(i have fished them frequently)
now, to answer the q i do not know of any personally in a tank, but have seen them for sale a lot of places and know htey are a hearty fish and immune ot many toxins and diseases, not sure about aquarium probs though