Why do reef tanks have blue lights?
Blue light in reef aquariums mimics the deep ocean to feed corals.
Most corals rely on tiny algae called zooxanthellae to produce up to 90% of their food through photosynthesis. Since water filters out red and yellow light, corals have evolved to thrive on the blue and violet light that reaches the depths. Specialized aquarium LEDs replicate these specific wavelengths to keep corals healthy and vibrant.
Nerd Mode
Coral reefs typically thrive in depths where the water column acts as a natural filter for the solar spectrum. According to the National Oceanic and Atmospheric Administration (NOAA), water molecules and dissolved organic matter absorb longer wavelengths like red and orange within the first few meters. This leaves the shorter, high-energy blue wavelengths, roughly 400 to 500 nanometers, to penetrate deeper into the ocean.Corals have a symbiotic relationship with dinoflagellates known as zooxanthellae, primarily from the genus Symbiodinium. These algae contain chlorophyll-a and chlorophyll-c2, along with accessory pigments like peridinin, which are specifically tuned to capture blue light for photosynthesis. Research published in the journal 'Nature' indicates that these algae can provide their host coral with nearly all of its metabolic energy requirements.To replicate this in captivity, aquarium manufacturers use Light Emitting Diodes (LEDs) that peak at the 450-nanometer range. This spectrum not only fuels the algae but also excites fluorescent proteins within the coral tissue, causing them to glow. This phenomenon, known as biofluorescence, may act as a natural sunscreen or a way to transform light into wavelengths more useful for the algae. Without this precise light intensity and spectrum, corals undergo 'bleaching,' a process where they expel their algae and eventually starve to death.
Verified Fact
FP-0009297 · Feb 21, 2026