“The small or nano aquariums, as they are called, are a significant part of the hobby, and in turn our business,” said Damian Hall, senior marketing manager at Massachusetts-based Hagen Group.

One of the coolest things about Mandalay Bay’s Shark Reef Aquarium in Las Vegas is standing inside a giant, clear acrylic tunnel surrounded by big, toothy sharks, stingrays, sea turtles and a host of ...