Building a bubble nest means that he's happy in his new home! Building a bubble nest is also done by instinct, and there doesn't have to be a female around for the male to make a nest. You don't have to breed him just because he's building a nest, if you don't want to. Most male bettas do build a nest from time to time. I had a betta once who had almost the whole surface of the water covered in bubbles! When I would do a water change, I would use a spoon to scoop out some of the bubbles, and put them in a plastic cup. After the water change, I would put the bubbles back in, and then the betta would re-build around the old bubbles. I thought that was better than making him start from scratch! But you don't have to try to save his nest if you don't want to. He'll build another one. My bettas stopped building nests when they were about a year old. They were still healthy and active, but they just stopped the nest building. I missed the nest when they stopped!
