Mating Ground

I am playing in Creative Mode and would like to move the mating ground. I have the little heart icon that is supposed to let you do that but when I click on it nothing happens. How do I use it to move the mating ground? The fish were "born" in various places. Does the tool move all original mating grounds to the new location or do I have to move them individually? If it is the latter how do I identify them? I can't see that they are marked.
Using Creative Mode click on the landscaping tool and you will see a heart. That is the tool for moving the mating ground. There is some explanation for this when you enter Creative Mode.