Then that smell,as CrappiePappy said smelled like over ripe watermelon,is what smell your looking for.I would assume then this smell is when they are only on the nest,and maybe goes away after they leave the nesting area am I correct.Ill be using my nose from now on trying this method.Ive never seen the bubbles,but maybe its true fish do have gas,how else would it get in the air over that area,That might sound funny, but who can say.