For their size, they are fairly aggressive. I used to work with one that would come after my hand every time I went to clean his tank (had that fish for a long time too). I think a 72 would be OK for him, as they arent very active. Lots of hiding spots, and keep the tankmates to a minimum- they will eat anything that will fit in their mouth, and a few things that wont. You may have an issue finding tank mates that are fast, and large, enough to keep with him that are still appropriate for a tank that size.