I forget the actual names of the fish... :
But as Ladycfii has said "breeding identical (or nearly identical) fish from the original group is always safe. Cross-breeding species may or may not produce fishies that will live.
If you get it right, you can come up with some fish that will live a little beyond adulthood and can be bred and sold for much more than the common fish, but it will take some trial and error (and some dead fishies)."