There's an interesting review article from 2022 about the subject of organic compounds that plants release to the water, and how they could enhance the wellbeing of the system (or e.g. the fish living in it)

Article Root-released organic compounds in aquaponics and their pote...

Fish: Nutrient Providers

• Fish produce waste rich in ammonia, which is toxic to them but serves as a critical input for the system. This waste becomes the primary nutrient source for plants after processing by bacteria.

Bacteria: Nutrient Converters

• Beneficial nitrifying bacteria play a vital role in converting fish waste into plant-usable nutrients. The process involves: Ammonia Oxidation: Ammonia from fish waste is converted into nitrites by Nitrosomonas bacteria. Nitrate Formation: Nitrites are further converted into nitrates by Nitrobacter bacteria, which plants readily absorb.
• This natural biofiltration ensures water quality is maintained for the fish while providing essential nutrients for plant growth.

Plants: Biofilters

• Plants act as "biofilters," absorbing nitrates and other nutrients from the water to fuel their growth. In doing so, they clean and purify the water, which is recirculated back to the fish tanks.
• This eliminates the need for artificial fertilizers and reduces water waste, as the system operates in a closed loop.