First off - Nurses are able to adapt to captivity better than most other species of sharks(especially requiems). Certainly as well as most benthic sharks -such as Bamboos, eppies & Horns.
While suggesting that a 100,000 gallons is a bare minimum for keeping a Nurse - maybe fine, and naturally very realistic - if you happen to own a small public Aquarium. But it's not very realistic figure for a private aquarist.
And while some aquarists can say that Nurse sharks - don't belong in the hand of any private aquarist. The reality is that Nurse sharks often end up in the hands of private aquarists.
The big problem I have - it that the species all too often end up in the hands of Inexperienced shark aquarists - which is a recipe for trouble. I really don't have a problem with Nurse Sharks being kept by very knowledge & experienced private aquarists. As I've heard of aquarists that have kept successfully - adult Nurses in 20,000-25,000 gallon shark lagoons. And even cases of breeding Nurses in a 30,000 gallon lagoon.
Ultimately it's impossible to exactly replicate the ocean (which is the ideal place for all species sharks). The best thing that any aquarist (public or private) can do is make sure all of the shark's needs are met in order to give it the best chance for survive in captivity.
