Well usually if he see's something colorful or shaped fish like then fish will think it is another fish. Like my betta as well. If you paint your thumb nail a bright color and put it facing him. He will follow your nail around or even flair at it, because he thinks it is another fish. You can just let him go along with it. But be careful, because he may jump out of the tank to get closer to what he thinks is the female. Betta's are known for their athletic jumps.