The really strange thing about this movie is that despite its strongly overt themes of anti-captivity, it triggered a huge boom in sales of clownfish.
A vast number of people seriously watched this movie and decided that they would go out and buy tropical fish.

(link)

About half of the tropical fish in pet stores are wild-caught.
In the five years following the movie’s release, the clownfish population on some reefs fell by 75%. The increased level of sedatives used to knock out wild fish caused lasting damage to tropical ecosystems.

Because many people did no research on how to care for tropical fish, many clownfish died as a result of inadequate living conditions.

When people got bored of caring for their fish, many of them were released into oceans where they were not native. Feral clownfish (among other popular aquarium fish) are even now harming the ecology in American oceans. (link)

So many people’s reaction to seeing a cute animal is “I want one!” This stems from the belief that animals are objects to be owned, not complex individuals with desires, needs, and lives of their own.
“I want one!” demonstrates a complete disregard of animal’s rights to live autonomously, and places the focus squarely on human desires.

Animal lives have higher standing than human whims.
Animals do not belong to us.
Fish aren't meant to be in a box.

Some solid commentary. Check it

Before looking into fish as a pet, read about what really goes into keeping them. Read about cycling, and that 1-in-per-gallon isn’t a real thing, and about the needs of each species as far as temperature, pH, planting level, substrate, level of water maintenance, the number of fish needed for schooling fish to thrive, food type and amount… If you can’t provide those, don’t get the fish. If two fish have disparate or conflicting needs, don’t keep both in the same tank. Fish can be happy in an aquarium- but what most people picture as ‘adequate’ is sorely incorrect.

Some species will NEVER thrive in captivity, and some require such extensive maintenance and such specialized tanks that only the most dedicated and experienced hobbyists should even consider it (looking at you, octopus and freshwater rays!)

Read about which species are farmed and have very low wild catch rates. Many popular aquarium fish fall into this category, like swordtails and (freshwater) angel fish. Freshwater fish in general have better numbers for farmed vs wild than saltwater and brackish, but that’s a generalization and each species should be researched. 

Some, like bettas and ornamental goldfish, can’t survive outside captivity- but they still have NEEDS. It’s tragic how often these two species in particular are neglected to death by small tanks and owners who have no idea what they require. Goldfish in particular are very dirty eaters and produce more waste than most other fish of similar size, and as a result need a lot of space with lots of room between the fish . A well-kept, happy goldfish with lots of space can reach >6″ long and live for DECADES. If you keep them right, fish are a real COMMITMENT of your time and resources.

If you can’t fulfill the needs of a fish, please PLEASE do not release it or toilet it. Try to rehome your fish first, there are resources for doing it on many large aquarium hobbyist websites!

 DO NOT TAKE WHAT THE PETCO/PETSMART/WALMART PEOPLE SAY AT FACE VALUE, THEY WILL LIE TO MAKE SALES. DO YOUR OWN RESEARCH.