Odd set of arguements you've got going there. To address your question in your second to last post- no, not exactly. As you have pointed out several times yourself, an aquarium is not nature, it is a glass box. That is why planning and assuring species compatability is important. I don't agree with euthanizing a fish as a first resort to dealing with compatability problems any more than I would agree that it is okay to put your dog to sleep because you can't get it to stop barking. That's just laziness and bad stewardship. You can call me a bleeding heart and make anthropomorphic nemo analogies all you would like but I don't think my opinion is any less valid than yours here.