First off, when I said that a 240 gallon would be fine for a Brownbanded Bamboo. But I didn't say a standard 240 gallon(8x2x2). The truth is your standard aquariums aren't really good for most species of sharks for "home aquariums", because they are generally to narrow.
I made the suggestion about the Brownbanded - because the fact is it's simple a much better choice(than a Nurse) for a home aquarium shark.
Most sharks for "Home Aquaria", like Bamboos, Horns, & Catsharks really need tanks build like the clam tanks you find in some LFSs. That is fairly shallow but wide & long.
And a adult Brown banded needs at least a tank that is 3 ft wide & about 7ft long.
By the way Zoodiver - yes, Nurse sharks can 14ft long - but remember encountering 14 ft nurse shark - is like encountering a guy like that over 7ft tall(unless you go to NBA games on a regular basis). Generally 99% of the sharks(of any given species) your going to see won't ever reach the maximum size of the species.
Also Remember, a species average is general the average size of all available adult specimens of that species. So if you take a fairly common shark like the nurse - your may have hundreds of adult specimens. And even in the wild the nurse shark averages about 3m(10ft).
And yes, Zoodiver, your nurse should still keep grow for several more years - nurses don't full sexually mature(general sign of adulthood in all animals) until they reach 7.5ft
long.
Personally I think sharks like Lemons, Nurses, & Zebras - should be banded from ever being sold to LFS - this guys simple get way too large for even experienced shark hobbists to keep. Yes, I believe that these guys are best seen at public aquariums
Also most requiem sharks like Blacktip & Whitetip Reef sharks, as well as Leopards should be resticted - requiring to the shark hobbist to show they have experience(ie must get a license or permit- to own) with smaller free-swimming sharks.
Only the following free-swimming sharks should be available to most shark hobbists, without requiring a premit or license. But even these still require a large shark pool(at least 10-15 on diameter), to keep.
- Atlantic Smoothhound - 4 ft long - at least 1,700 gallons
- Brown Smoothhound - about 3 ft long - at least 1,200 gallons
- Grey Smoothhound - about 4 ft long - at least 1,700 gallons
- Dogfish - about 4 ft long - at least 1,700 gallons.
Note that smoothhounds are mostly free-swimmers - but also can rest on the bottom for brief periods.
- Atlantic Sharpnose - about 3.6 ft long - at least 2,100 gallons
- Bonnethead - about 4.5 ft long - at least 3,200 gallons
Both of these species are true free-swimmers (Ram Ventilators).
And when planning to keep any shark in your home - remember - Bigger is always Better.