Mine will eat from the top, the bottom, the middle, lol. They are pigs. What you can do is put them in tank water in a bowl, let them soak a bit, pinch them with your finger and they will sink.
I feed all of my current FH sinking pellets, but they can easily be trained to eat floating as well. When you feed your sinking pellets, feed one at a time, and make the FH come to the surface to take them. He'll catch on soon enough, then simply switch out the sinking for the floating.
What you can do is put them in tank water in a bowl, let them soak a bit, pinch them with your finger and they will sink.
The problem with that method is a lot of the water soluble nutrients will leach out in the water, and again when you squeeze the air out of the pellet.
Floating pellets are designed to hold air (via small honeycomb pockets) so they will float. Most larger fish also find them more palatable as due to their design they tend to soften up quicker than sinking pellets.
Your fish is still young, not to worry, it can be trained to eat whatever you want it to eat.