GM "Glofish" Zebrafish Outcompeted by Non-GM Zebrafish

I think most biologists would agree that genetic diversity is key to survival, and that most biologist would agree that "monoculture" of anything is risky. If these genetically modified fish were to make it into public waters, which is very likely, what's the worst that can happen? Chances are they won't survive very well, and as the article suggest, will be outcompeted. The mentions that this caused the disappearance of the transgene from the fish population over time. Do we really want this gene floating around that has been designed in a lab any way?