Ohh...
Kept them in no higher than 1.010, with a pH of about 8. I've kept them twice before.
In my experience, they are not too difficult to keep in the proper salinity. Unfussy, and will accept most foods eventually. Not too sensitive to water params, but not invincible either. They are predatory, though pretty peaceful alongside fish too large to be eaten. They are also pretty fast growers. A standard 55G will do a group of 3 or so well for a couple of months, but at full size, you should be looking at 100G or more for a group. Definitely schoolers.
I would also advise caution against keeping them with aggressive fish like puffers and morays-- unless they are very well-fed, you'll likely start to see some bite marks on your sharks sooner or later