It all depends. If you do, are there any places on the surface of the pond that are completely still. If so, you need more. If yes, you need more.
Fish require oxygen in the water to breath.
If the oxygen is depleted, the fish simply smother. You may have happy fish during the daylight hours with enough bubbles to go around - but it becomes a different world at night. Plants, who choose the night as their time to grow, rob the water of oxygen. This is when it's needed most. In mid summer in mid day temperatures soar and there's no relief for you.