There has already been a post on this I think. Are these the same as "glofish" (www.glofish.com) they seem similar.
anyway, IMO, it isnt as bad as dyeing, as it doesnt harm the fish.
(quote from website)
"Taikong insists the GM fish, designated TK-1, is safe, sterile and that its additional fluorescent gene is harmless."
(end quote)
I would be more worried about the usual ramifications of genetic modification: i.e: how do we know its safe, what if there was somthing they missed and the fish reproduce or take over an ecosystem, or somthing like that.
Edit:
sorry, read the article a bit better:
they say at the bottom:
"in particular, some tropical fish are being bio-engineered to tolerate cold and could colonise UK waters if they escaped, disturbing the present ecosystem."
and also
"According to Derek Lambert, of Today's Fishkeeper magazine, GM piranhas could survive in our waterways and pose a major problem. He is urging traders to boycott the TK-1."
this guy says:
"Keith Davenport, of the Aquatic Ornamental Trade Association (AOTA), commented that interfering with the genome was unnecessary and said people did not want animals to become fashion accessories."
(my opinion: they arent going to be any more a fashion accessory than any other ornamental fish...unless people start wearing "betta necklaces" with bettas in a little jar on the necklace....NO LETS NOT GIVE ANYONE ANY IDEAS!!!! sorry!)
So in summary i think the GM is more an issue than cruelty.