Autotrophic Feeding
Autotrophic feeding describes how many corals produce their own energy internally, rather than relying solely on capturing and consuming food from the water around them. This is made possible by zooxanthellae, single-celled algae that live symbiotically within coral tissue and generate energy-rich compounds through photosynthesis, which the coral host then uses to support its own metabolism and growth.
For many of the most commonly kept stony corals, autotrophic feeding is the primary energy pathway, making lighting one of the most important factors in their long-term health.
Why It’s Important
- Serves as the primary energy source for many SPS and LPS corals commonly kept in reef aquariums.
- Reduces, though doesn’t eliminate, a coral’s dependence on active target feeding.
- Ties coral health and growth directly to lighting quality, spectrum, and duration.
- Forms one half of a broader nutritional balance alongside heterotrophic, or food-based, feeding.
How It Works
Zooxanthellae embedded in a coral’s tissue photosynthesize using available light, converting it into sugars and other energy compounds. A significant portion of this energy is shared directly with the coral host, effectively allowing the coral to run much of its metabolism on light-derived fuel rather than captured food.
Because this process depends entirely on adequate lighting, both in intensity and spectrum, autotrophic feeding capacity varies significantly between coral species and even between different parts of the same colony depending on how much light reaches them.
This relationship also has a stress dimension worth understanding. When a coral experiences significant stress, from overheating, poor water quality, or other disruptions, it can expel its zooxanthellae in a process known as bleaching, effectively shutting down its autotrophic energy supply. A bleached coral isn’t necessarily dead, but it loses its primary energy source until it either recovers its symbiotic algae or is otherwise supported through heterotrophic feeding in the meantime.
Autotrophic Feeding and Related Parameters
Autotrophic feeding is closely tied to PAR and photosynthesis, since both determine how effectively a coral’s zooxanthellae can generate usable energy. It’s also directly connected to zooxanthellae themselves and stands in contrast to heterotrophic feeding, the process by which corals capture and digest particulate food. Most healthy reef systems rely on a combination of both feeding strategies rather than either one alone.
Common Misconception
A common misconception is that strongly photosynthetic corals under good lighting don’t need any additional feeding. In practice, most corals benefit from at least some heterotrophic input, whether through broadcast feeding, target feeding, or dosed amino acids and proteins, since autotrophic energy alone often isn’t sufficient to support maximum growth, tissue repair, and vibrant coloration.
The Bottom Line
Autotrophic feeding is the process by which corals generate energy internally through their zooxanthellae’s photosynthesis, making lighting a central factor in their care. While it covers much of a coral’s energy needs, pairing it with appropriate heterotrophic feeding gives corals the fuller nutritional picture they need to truly thrive.
