Funny thing is that three spined sticklebacks are popular European native fish, I've seen them in the the aquarium books. If I obtained three spined sticklebacks from saltwater then convert them to the freshwater, can they breed in the tubs?
Although I have converted threespines collected in saltwater to freshwater, I have not bred them.
Since some populations are considered anadromous, and others are landlocked in freshwater, in theory, it should work.