Remove the food after a few minutes. It is not good for the water quality of a tank that size. Or any tank for that matter.
bubble nests are not a good gauge of when they are happy since some will even make them in the petstore cups. They are more the male saying hey I am ready to breed. By no means should you actually give him a female fish though! But it can also be a sign that the water is favorable. There are other reasons he made a bubble nest, but I notice nests more when they like their conditions. But its not again its not nessarily saying they are happy. There are other reasons they do it.