Well here I can offer a little assistance
In Scotland the laws governing the land are different from England. I can only speak for Scotland but the laws are roughly as follows
This is not exact but as I can not remember the exact definition but basically any person who : Tortures, Injures, Kicks, Overloads, Terrifies, Ill treats, Over-rides or neglects any of the following animals is guilty of an offence
Sheep, Horse, Ass, Mule, Pig, Ox (Cattle), Goat, Dog, Fowl or Cat (Plus the catch all) ANY CAPTIVE ANIMAL
Fish would definatley fall under the ANY CAPTIVE ANIMAL bracket, but if allowing your fry to be consumed by larger fish constitutes any of the above, well its open to arguement really.
The above legislation is not ver batum and only intended as a rough guide, I will locate the exact legislation tonight and post about 23.00 hours.
There may well be legislation in place that specifically covers fish and the selling and care of such, the above was intended to cover your average house hold pets and farm animals but again, any captive animal does cover fish and there is stated cases in law relating to fish.
Regards,
Hec