I don't believe that to be correct OF.
Most of the "fancy goldfish" strains have been line bred to their current state over centuries. There are hardly any that would survive a season in the wild, indeed, the most extreme examples have to be seriously mollycoddled in order to survive in captivity. That is not life, that is simply existance, an example of what I believe could be in the pipeline if GM is not kept under control. The difference with GM is that a lot of these things could be created within a year or less - there is no way you could start with non-domesticated carp and breed, through selective breeding, a "bubble eye" goldfish in that time frame. You'd be lucky to create a "goldfish" that bred true in a decade.
Flowerhorns and other hybrids are relatively easy to produce because they do not require very high tech systems, just add some fish from geographically isolated populations and see which will breed with which. Put a positive spin on it, hype them, and away you go. The danger with some of the hybrids is that unlike mules, they can be viable breeders, thus they pose a threat, and I oppose the hybrid trade for the same reasons. There have been incidents in the far east, Malaya in particular where this has already been an issue.
With GM, there is always the chance of the modification escaping into the wild. I agree, the particular modification made to these creatures is not likely to enhance their survival, thus they are unlikely to pose a threat to species, but read the rest of what I said above. The perceived "demand" for these things WILL attract medium sopisticated laboratories who, probably as a side effect, may see ways of offsetting costs by producing weird "items" they may be able to sell to a gullible public.
As for the survival of alien species a long way from home, just read the literature. It is full of cases where an "X" from "Y" was suprisingly found living in "Z". In the "London Apprentice" pub in Isleworth, SW London, is a collection of stuffed fish rod caught from their terrace. One is a Megladoras irwinii.
Don't get me wrong, I am not an opponent of GM per-se, but I believe it should be carefully controlled until it is a mature technology. I don't believe creating weird items for the pet trade is a productive use for the technology.