How do we know this?

[florida joe]

I have read numerous threads that discourage hobbyists from keeping certain type of fish in their aquarium because the fish need X amount of room to swim. So my question is how we know that a certain fish need 6 feet of horizontal room to survive in our tank. Why not 6’6 or 7 ft. now I am sure some hobbyists will say that they are talking about the minimum. But how do we really know. And while I am on the subject. Now do we know what the real potential of growth in a fish is? There are no real studies I can find that gives a definitive answer

 

[snakeblitz33]

I think a lot has to do with empathy. Ever seen a full grown naso tang in a 55g four foot tank?
Ive kept a 12" freshwater oscar in a 20g before, but he looked really depressed. Therefore i think its more empathy then actual studies done.
Ive also kept different tangs in 4ft tanks without problems. Ive also kept fish combinations in reef tanks that "arent supposed to go together and are not reef safe" ie butterflys and angels. There is risk - and many of us on thr forums dont want to tell someone "the wrong thing" for whatever reason.

 

[fishhead80]

It's like the desperate housewife gossips.. Information gets passed on from one hobbyist to the next. It's just what we've read and heard from others who are in the hobby. Of course we dont want to pass on wrong info, so we just keep repeating what were told or read. I myself kept a Scopas tang and foxface in a 4ft 90g tank for over 4 yrs and they both look happy and healthy. It didn't grow much though. Problably cuz I only fed once a day.

 

[xcali1985]

A lot of people try to mimic the natural environment for a fish. Tangs in the wild swim in open waters and can do so for miles. Same with Stingrays and Sharks. However, if you closely pay attention to your tank you will notice that in your our setups the lack of vast open waters, doesn't normally entice them to try to. Instead you end up with fish that pick at the rocks and duck in and out of the rock work.
I think when it comes to tangs and some of the other larger species, tank design has more to do with keeping them happy than sheer size.
You can put a shark in a 3' cylinder tank and it will be happy because it can swim in constant circles mimicking open water swimming. If I was to ever house those creatures or a fish that got above 18" I would probably look into a cylinder tank.