Aquariums are fascinating to look at, filled with a variety of colorful fish swimming around in an enclosed, artificial ecosystem. One particularly eye-catching sight that can often be found in aquariums are glowing or fluorescent fish. These fish have the incredible ability to glow or fluoresce under certain lighting conditions, almost like living nightlights in the aquarium. But what causes these fish to glow and which species exhibit this trait?
What Causes Fish to Glow?
The glowing or fluorescence seen in certain aquarium fish species is caused by fluorescent proteins in their skin and scales. These proteins have the special capability to absorb light energy and then re-emit it as a different color of light, creating an eye-catching glow. There are several different fluorescent proteins that can produce light in the red, green, and orange/yellow color spectrums.
The most common fluorescent proteins found in glowing fish are:
– Green Fluorescent Protein (GFP) – This causes a green glow and is found in fish like green tetra.
– Red Fluorescent Protein (RFP) – This protein creates a red glow and is present in tetra fish like the bloodfin tetra.
– Fluorescent proteins in the orange/yellow color range – These can create yellow, orange, or reddish-orange hues and are seen in fish like the laser corydora catfish.
How Do Fluorescent Proteins Work?
Fluorescent proteins have a unique molecular structure that allows them to absorb higher energy, short wavelength light and then re-emit it as lower energy, longer wavelength light. This causes the striking glow from the fish’s body.
Specifically, fluorescent proteins contain a chromophore group in their molecular structure. The chromophore contains conjugated double bonds that can absorb incoming light energy. When the chromophore becomes excited, the energy gets distributed across the conjugated bond system. Then as this energy is released, it creates the fluorescent glow at a different wavelength than the initial absorbed light.
By genetically encoding the instructions to produce fluorescent proteins, certain fish species have evolved this trait as a means of underwater illumination and communication. The vibrant glow can help with schooling, mating, camouflage, and predator avoidance.
Glowing Fish Species in Aquariums
There are a number of freshwater and saltwater fish species that exhibit biofluorescence or a glowing effect under aquarium lighting. Some of the most popular glowing fish kept in home and public aquariums include:
Freshwater Fish:
– Green Tetra – Small neon tetra species that glows bright green under blue actinic light due to GFP proteins.
– Bloodfin Tetra – Active schooling tetra with red fluorescent markings on fins due to RFP proteins.
– GloFish – Genetically modified zebra danios that express jellyfish GFP proteins to glow red, green, orange, blue, or purple under UV light.
– Laser Corydora – Catfish with bright orange/yellow fluorescent patches along its head and body.
– Blue Gourami – Labyrinth fish that can display a blueish fluorescent sheen.
Saltwater Fish:
– Seahorses – Many seahorse species glow yellow/orange due to fluorescent proteins.
– Anthias – These colorful reef fish often fluoresce in reds, greens, and oranges.
– Parrotfish – Parrotfish scales contain fluorescent purines that give a yellow/green glow.
– Scorpionfish – Biofluorescence helps provide camouflage among coral reefs.
– Anglerfish – Glowing lures are used to attract prey.
| Fish Species | Glow Color | Fluorescent Protein |
|---|---|---|
| Green tetra | Green | GFP |
| Bloodfin tetra | Red | RFP |
| GloFish danios | Red, green, orange, blue, purple | GFP from jellyfish |
| Laser corydora | Orange/yellow | Unknown orange fluorescent protein |
| Seahorses | Yellow/orange | Unknown orange fluorescent protein |
| Anthias | Red, green, orange | GFP, RFP |
Ideal Lighting for Maximum Fluorescence
To maximize the fluorescent glow from biofluorescent aquarium fish, specific types of lighting are recommended:
– Blue Actinic Lighting – Actinic lights emit wavelengths of light in the short blue spectrum which powerfully excites the GFP proteins to emit the most vibrant green glow.
– UV Lighting – Ultraviolet light sources contain the highest energy waves that can stimulate peak fluorescence across multiple color spectrums from fish.
– Blacklights – Blacklights or UVA lamps emit longwave UV rays that bring out strong, otherworldly fluorescence from fish scales and skin.
– High Intensity LEDs – High output LED lights in colors like cyan, violet, or UV can enhance biofluorescence.
Using lighting centered in the blue and UV ranges will generate the strongest fluorescent effects in aquarium fish that have these proteins. The proteins absorb the high energy waves and re-emit them at a visible, lower frequency color for a bright glow.
Feeding Tips for Healthy Fluorescence
To help maintain vibrant glowing coloration, fluorescent aquarium fish require a balanced, nutritious diet:
– Algae-Based Foods – Spirulina flakes or pellets provide essential pigments and minerals for enhancing natural fluorescence.
– Brine Shrimp – This staple fish food contains carotenoid pigments that help replenish fluorescent proteins.
– Color-Enhancing Supplements – Products like coral food or garlic supplements provide nutrients that optimize fluorescent coloring.
– Varied Proteins – A mix of proteins like mysis shrimp, blackworms, and beef heart support overall health.
By feeding a mixture of pigment-enhancing prepared foods supplemented with proteins, aquarists can maintain and maximize the natural brilliant fluorescence of their fish.
Breeding Fluorescent Aquarium Fish
Selectively breeding fish with particularly intense or vibrant glowing traits can help propagate fish with stronger levels of biofluorescence:
– Start with a proven pair showing intense fluorescence.
– Provide excellent water quality and nutrition to optimize breeding health.
– Raise fry under lighting that enhances fluorescence so it develops strongly.
– Selectively breed fry that exhibit the strongest glow colors as adults to reinforce the trait.
– Partner offspring from the brightest individuals for successive generations.
With each successive generation bred from highlighters showing maximum fluorescence, the biofluorescent traits can become stronger and more pronounced through this selective process.
cautions to take as part of aquarium ‘s responsibile owner
While fascinating to observe, biofluorescent fish do require some special considerations:
– Overexposure to intense lighting can cause excess stress on fish. Provide shaded areas and intervals of darker lighting.
– Monitor water parameters closely since conditions like pH changes can affect fluorescence.
– Avoid mixing fluorescent varieties since crossbreeding can diminish their unique glow patterns.
– Don???t mix with aggressive tank mates that may nip fins and damage glowing features.
– Purchase captive-bred specimens whenever possible, not wild-caught fish.
When kept responsibly with their needs met, biofluorescent fish can display their incredible glowing qualities for years in home and public aquaria. Their brilliant hues and colors make them living works of art.
Conclusion
The glowing or fluorescent fish commonly seen in aquariums derive their unique shine from specialized fluorescent proteins in their skin and scales. These proteins efficiently absorb high energy light waves and re-emit them at a lower frequency, creating a striking luminous glow. By providing the right aquarium lighting, foods, tank mates, and care, aquarists can maintain and enhance the dazzling fluorescent effects of these marvelous fish. When viewed under the right conditions, they are truly a sight to behold.