This is absurd.
However, the petion makes the wrong case, IMO. It makes a case that is too 'extreme' for the government to really be interested in, given the institutionalised and deeply ingrained abuse done to fish.
The petiton asks for a ban on pets (in this case goldfish) as prizes. It doesn't directly tackle the living conditons of the fish other than to lend weight to the case for the ban. Perhaps if the petition asked for licensing for those wishing to give animals as prizes, and if the petition asked for quite strict welfare conditions for the animals, without asking for an outright ban.
I agree that their should be a ban, but clearly the government doesn't.