It is believed that aquarium has two function what entertainment and education. But the most important function is research. Everybody most forgets necessary money to research. So dolphins make you fun by a aquarium. If every creature should spend them life naturally, do you consider about unnatural animals, like cats and dogs. 
Do you believe better that people give up spending life with cats or dogs. 
There is a opinion what cats or dogs were broken until DNA by humans. Do you like cats or dogs? 
They are remade as humans want. Is it natural?

Aquariums are considered to have two functions: entertainment and education. The most important function, however, is research. However, many people forget to fund research. That is why dolphins entertain you in aquariums. If all creatures should spend their time naturally, what about unnatural animals like dogs and cats?
Do you think people should give up spending time with cats and dogs?
Some people believe that dogs and cats have even had their DNA destroyed by humans. Do you like dogs and cats?
They are being remade to be what humans want them to be. Is that natural?