Well, by seperating out your larvae and rearing them without predators aren't you taking away survival of the fittest? By not keeping your adult pets with predators aren't you also preventing a "natural" process? People have been modifying and interfering with nature for thousands of years, I don't see why now, when we can suddenly do it faster and more efficiently, it has to become some sort of ethical debate. Glowing axolotls, and other glowing animals are not only a good proof of concept, but may also do greater things, like displace the demand for wild caught animals. And what's more, with glow in the dark animals, incidents like the "teenage mutant Ninja turtle incident" (the popularity of teenage mutant ninja turtles caused children around the world to buy red eared terrapins by the millions, when the terrapins out grew their enclosures they were often released, becoming established in parts of europe and having dramatic environmental consequences), because there would be next to no chance of the glowing animals becoming established in the wild. GM could not only give us more crops but for example we could genetically modify algae to produce bio fuels or sequester carbon more efficiently than any plant in the wild, we could create viruses targeting pest species and invasive species (we've already done this to a small degree), we could create species that would facilitate deep space exploration and colonization, and going into more controversial territory, we could eliminate Sickle cell, Cystic fibrosis, maybe even some forms of depression and cancer. The possibilities are endless, and if it weren't for this wealth of potential, I wouldn't want to be a biologist.
People often argue that GM populations would be more vulnerable to disease, but I don't see why this would have to be the case. Sure if every GM crop were a clone of the last this would be true, but we can make it so that GM crops are genetically diverse, we can also possibly genetically engineer new strains in the face of a disease faster than the plants would adapt naturally. Sure there's the odd mishap, such as the issue with brazil nuts and allergies, but these are often sensationalized. Journalists are looking for genetic frankensteins because it makes for and interesting story and sells more articles. The truth is, as Matt Ridley states in his book The Human Genome, those Brazil nuts had the potential to benefit a lot more people than they would harm, but the media jumped on it and smothered it.
Some people think genetics will result in eugenics, nonsense, nazism causes eugenics. I don't see why it's such a hard debate, please enlighten me. I see GM playing an essential role in a brighter future.