Yeah -they seem to do best in small schools.
Mattiej kept a small school (4) Atlantic Sharpies for in his shark lagoon, for about 4 years. So for lagoon size need for a small school (3-5) of these sharks - at least 500-550 sq.ft, with a volume of at least 15,000-16,000 gallons - or roughly the same size as you will need for adult Bonnetheads. Pacific Sharpies are a bit larger and likely would require a lagoon large enough to keep an adult Blacktip Reef.
Btw - as for what these sharks look like - check my avatar - that's a Sharpnose.