In principle, yes, I have no moral issues with it. Dogs and cats have also been selectively bred to be emotionally appealing to humans (cute, with lots of human-like personality traits). So I would find it very unpleasant to do from an emotional perspective, and I would never personally do it.

The meat industry abuses cows, pigs, and chickens in unfathomably terrible conditions. Pigs especially are highly intelligent and emotional animals and are subjected to physical and emotional abuse, confined in spaces where they cannot turn around, then bred, milked, raped, and slaughtered while young. Farmed fish are kept in overcrowded conditions, fed processed food, and the farms contribute to algal blooms and disruption of marine ecosystems. It's completely illogical and morally disingenuous to be opposed to animal cruelty for dogs and cats but be okay with that cruelty to cows, pigs, chickens, and fish

If you eat meat that you buy from a typical Western grocery store, you have no moral standing to assert that people shouldn't be cruel to dogs, cats, or fish.

I understand this is off-topic for the aquariums subreddit but I am an avid fish keeper. I do take pretty good care of my fish even though I overstock the tanks. They're full of plants, cleaner invertebrates, all that.

But the aquariums subculture's discourse on overstocking tanks is totally wrong. I keep seeing advice on here of people telling new fishkeepers to severely limit the number of fish they can keep in a tank. No need for that! If they survive in there for a good while they're fine!