(i just cut + pasted from other forum cos i'm so busy)
I'm not against crossbreeding,
I am against INbreeding and selective breeding for traits that are detrimental to the fish.
Like i said, i don't know much about it, but i have the idea that widening the genepool (like in the wild) for fish that have been selectively breed for pet shops(leopards + guppies) by letting them breed with a hardy, wild fish will give them a sort of hybrid vigor.
I get this idea from the fact that crossbreed dogs, horses, and cats (the animals i have experience with) are generally more robust, mentally superior (alert, cautious, etc) and less suceptible to illness.
BUT, i am not actually trying to crossbreed, they are just in the same tank, if they don't breed, it's not meant to be. It's a big tank and they do have partners of the same species.
And if they did crossbreed, and the offspring looked deformed or sickly, i wouldn't allow it to happen again.
---As for leaving nature to it's own devices, fish naturally have acess to other (similar) species, and this is the part i'm not sure about..which ones are compatible, and how likely a crossbreed is to occur in the wild.
What i really meant by that comment is that it's wrong to pick out the "cute" "funny" "whatever" fish, and breed from them, when the selected feature would compromise survival of the fish in the wild.
I think it's really sad that people breed things like celestial goldfish, to me they look sickly, pathetic, and in pain (if fish feel pain...but don't get me started on that)
Sorry for rambling, i'm just in a hurry