While I don't quite agree with rattler's philosophical perspective, I think there's definitely some practical wisdom to it. These are not rare or fragile creatures - they multiply by the dozens and their populations can go from 7000 to 120,000 in a matter of months. Animals that breed this fast do so because they're meant to live in environments where most of their young might be picked off by predators or die as a result of harsh conditions. We're not talking about bison or redwoods here.
I think it would be prudent to attempt to maximize the chance of success before bringing the fish in - I don't think there's much merit in naive or unprepared experimentation - but the loss of a few small fish that are vigorously invasive pests in other parts of the world is not so worrisome. It's not making a dent in their endemic populations so ultimately it's neither hurting the environment as a whole nor is it really subjecting the individuals to any sort of unusual cruelty. My biggest hesitation comes from the possibility that they may escape into the wild and disrupt other critters that occupy a similar niche, as they've already been known to do.