Many people opt for colorful fish in their aquariums.

We have the neon chicken with bodies and bright red stripes, a variety of Guppies of different color or the goldfish which, contrary to their name, do not always have only gold scales.

A particularly striking, but also incomprehensible freshwater fish is usually popular among amateur and the aquarium trade.

The ghost catfish or glass catfish is scale-free and is usually described as pigment-free and transparent. Their scientific name is kryptopterus vitreolus; “Kryptos” and “Pteron” are Greek for “hidden” and “wings” respectively, while “vitreolus” comes from the Latin word “vitreus”, which means “glass”.”

Pretty awesome, right? But their strange appearance is not all they have to offer, because when the light hits your body just right, your body becomes iridescent.

The ghost catfish can transform your aquarium from a macabre atmosphere into a delight in a matter of seconds. Ghost catfish are also known for their scholastic nature, so imagine that several of these fish show their colorful glow in an aquarium at once.

But what exactly causes rainbow reflections in ghost catfish?

The iridescence in fish is usually caused by the light reflected by the textures on the surface of their scales. But as I mentioned earlier, ghost catfish are dandruff-free. In addition to being free of dandruff, ghost catfish are also transparent, so that light can always through their body. Where exactly can the light be reflected in their tiny bodies?

The researcher went in search of the answer about how the ghost catfish creates its iridescent glow.

Simply put, a study has found that the ghost catfish gets its iridescent glow from its internal organs rather than from its non-existent scales. The muscles of these tiny fish cause the light waves to bend, which results in bending which then creates this striking rainbow effect.

“The iridescence results from the collective diffraction of the light after its passage through the periodic ligament structures of the sarcomeres, and the muscle fiber thus act as a transmission network,” says the study.

Because the ghost catfish skin is able to let more than 90% of the light directly through the muscles, the diffracted light can leave the body.

What makes the ghost catfish unique is its transparent skin. Other species also have the same type of muscle, but we cannot see iridescence because they are not transparent.

Although it is still unclear why the ghost catfish has this ability, the researchers believe that it could be a form of camouflage to avoid predator or that it could be used as a communication signal in these species of schooling fish.

Read here for more rainbow-colored creatures, or watch the video below to see the ghost fish show off their iridescence.