in congested singapore, its something you have to live with, if you say like that, actually all fishes grow well in pond, so don't have any pets at all, dogs need space to run, cats also, birds need to fly, turtles need the ocean, etc blah blah blah..
Y have any pets at all in the first place if you think that way? maybe u should watch nemo
anyway this is an often debated topic..