You know, there are plenty of people all over the world who keep "GOLDFISH" ponds...with no worry whatsoever of the goldfish going anywhere. I see no reason that if Pinks has a pond that he made on his property for his own enjoyment...same as any goldfish pond....he aught to be able to put what he wants in it. He seems fairly certain there are no issues with the fish escaping into the wild.
Pinks, if the water is healthy and you don't mind them eating your guppies/minnows/tadpoles....lol...I see no problems with keeping them in there temporarily until they can grow to a good size for your tank.

Pinks, if the water is healthy and you don't mind them eating your guppies/minnows/tadpoles....lol...I see no problems with keeping them in there temporarily until they can grow to a good size for your tank.