The form of hydroponics that does not require a growing medium at all is

The correct answer is Aeroponics.

To understand why this is the correct option, let's break down the different forms of hydroponics listed in the options:
1. Aquaculture (specifically in the context of hydroponics/aquaponics): Often involves growing plants in water with aquatic animals, which serves as the medium.
2. Static solution culture: Plants are grown in containers of water containing nutrients, where the roots are submerged directly in the liquid nutrient solution. While it doesn't use a solid substrate, the liquid itself acts as the growing medium.
3. Medium culture: As the name implies, this method explicitly uses a solid, inert growing medium (such as sand, gravel, clay pebbles, or coco coir) to support the plant roots and hold moisture/nutrients.
4. Aeroponics: In aeroponics, plants are suspended in a closed or semi-closed environment. The roots hang freely in the air and are periodically misted or sprayed with a nutrient-rich water solution. Because the roots are suspended directly in air without any solid or liquid support structure holding them, it is the form of hydroponics that does not require a growing medium at all.