Light in reef aquariums

The importance of light in reef aquariums

Introduction

Light is one of the main resources supporting life on our planet. Being photosynthetic, many marine invertebrates need light to live: their symbiotic zooxanthellae need light for photosynthesis, to produce enough nourishment both for their own use and for the host coral.

1. 1Light drives photosynthesis
2. 2Host coral houses the algae in its tissue
3. 3Zooxanthella symbiotic alga that photosynthesises
4. 4Food up to 90% goes to the coral
5. 5From the coral carbon dioxide and water

Zooxanthellae use light to make food for themselves and for the coral.

Sources: [1]

1. 1Sunlight enters at the surface
2. 2Red the first colour to vanish: it does not reach 100 m
3. 3Blue the colour that reaches deepest
4. 4Below 200 m there is almost no light

Water absorbs red first, then yellow and green; blue goes deeper. Only the 100 and 200 m depths come from the sources: the lengths of the rays are indicative.

Sources: [2] [3]

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Sources

1. NOAA National Ocean Service (2026). Corals Tutorial: What is Zooxanthellae?. National Oceanic and Atmospheric Administration.
2. NOAA National Ocean Service (2026). How far does light travel in the ocean?. National Oceanic and Atmospheric Administration.
3. NOAA Ocean Exploration (2020). Why are so many deep-sea animals red in color?. National Oceanic and Atmospheric Administration.