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Fish tanks are soothing, until researchers start probing for answers and partygoers turn them into playful distractions. That’s when the bizarre fish stories begin to unfold… and take a decidedly strange turn.
Outside the realm of labs and fish-related hospital visits, some of the most captivating stories originate from public aquariums. From groundbreaking rescues to the puzzling case of a shark left at a worm farm, you’ll never look at a fishbowl the same way again.
10. Fish Pedicures with a Twist of Infection
A popular way to exfoliate feet is by getting a fish pedicure. Clients dip their feet into a tank filled with small fish that nibble away at dead skin cells.
In 2018, a woman in New York allowed Garra rufa fish to nibble on her toes. Months later, her toenails cracked, revealing the underlying layers.
Despite experiencing no pain, she waited six months before seeking medical attention. She was eventually diagnosed with onychomadesis, a condition where nails stop growing and eventually fall off. After ruling out other possible causes (such as injury or a family history of nail issues), this woman became the first known case linked to a fish pedicure.
In the past, Garra fish have tested positive for various bacteria that cause skin and tissue infections. Hygiene issues also arise as the tubs containing fish can’t be thoroughly sanitized between clients. Sanitary concerns include the risk of individuals with foot diseases using the tub before others.
9. The Oldest Fish in Captivity
In 2018, an Australian lungfish at the California Academy of Sciences' Steinhart Aquarium in San Francisco marked her 80th birthday. Having arrived as an adult in 1938, her true age is closer to 90. Named Methuselah, she is 1.2 meters (4 feet) long.
The oldest fish in captivity has a fondness for figs, prawns, belly rubs, and some specific volunteers. Methuselah also prefers her own tank. When placed in a larger aquarium with two younger lungfish, she insisted on swimming upside down until they relocated her back to her own space.
Genetics contribute to her impressive lifespan, but lungfish are exceptional in other ways too. These ancient creatures, dating back 400 million years, use a swim bladder to float and breathe air. Some even walk across the ground in search of new ponds.
Methuselah appears eager to live to a century. According to her caretakers, she has a hearty appetite and enjoys interacting with people. Because of this, the aquarium's pampered group of lungfish is affectionately known as 'underwater puppies.'
8. Fish Have Distinct Personalities
In 2015, scientists took on a challenging question: Do fish have personalities? To find out, they created a horror-themed experiment. They startled guppies by plunging a fake heron beak into the water. Another time, they introduced 'Big Al,' a carnivorous cichlid fish that would suddenly appear on the other side of the glass.
A guppy placed in this frightening setup had only a small plastic cover as shelter. After experiencing extreme terror, the fish was returned to a safe tank filled with other guppies. Three days later, it would return to the fear-inducing environment for another five-minute ordeal. This cycle continued for a month.
After exposing 105 guppies to this experiment, scientists concluded that the fish indeed had personalities. Each reacted in its own way, whether by hiding, fleeing, or freezing. The guppies repeated these behaviors during each encounter with the heron and cichlid every three days.
7. The Catfish Drinking Challenge
In 2016, a drunk man arrived at the emergency room with a strange injury. That evening, the 28-year-old, whose name wasn't revealed, had been partying with friends in Rotterdam, Netherlands, and decided to swallow live fish for fun.
Several goldfish from a home aquarium were swallowed with no issue. However, someone suggested trying a different tank resident—a small catfish. This was a Corydoras aeneus, a toxic fish with spines that stiffen and release venom when threatened to avoid being eaten.
Unsurprisingly, the spiky fish became lodged in the man's throat. He began choking, vomiting blood and beer—yet no fish came out. His drunken friends tried the Heimlich maneuver incorrectly. The man attempted to wash the fish down with beer, ice cream, and honey. After waiting hours, he eventually went to the hospital.
Delicate surgery eventually removed the deceased catfish, which was then preserved at the Rotterdam Natural History Museum. It now forms part of an exhibit showcasing remarkable encounters between humans and animals.
6. Wrasse Can Recognize Themselves
There’s a simple test for self-awareness: A mirror is used to place an artificial mark on the subject's body. If the subject reacts by touching or rubbing the mark, it suggests they recognize the reflection as their own body. Animals that have passed this test include dolphins, chimpanzees, elephants, pigeons, and crows.
In 2018, researchers aimed to find a self-aware fish. They chose the cleaner wrasse, a species known for its ability to notice unusual spots on other fish while feeding on parasites, making it an ideal candidate for the test.
When 10 wrasse were placed in individual mirrored tanks, things quickly became intriguing. Initially, they mistook their reflections for competitors and fought with themselves. But within a few days, they began performing 'friendly dances' in front of the mirrors.
Wrasse are typically solitary and don’t engage in dance with other fish. While it's difficult to confirm, they may have been dancing simply to observe their own movements. When colored gel was applied to their heads (visible only in the mirror), seven wrasse spent more time in front of their reflections or rubbing their heads against objects in the tank.
5. Fish Floaties
Leafy sea dragons are like seahorses that overindulged in plant fertilizer. These fish are entirely covered with leaf-like fronds, giving them a striking, leafy appearance.
In 2018, the Florida Aquarium in Tampa welcomed three young sea dragons. While keeping an eye on these Australian fish, the aquarium's vet observed a troubling issue: the fish were eating poorly and kept sinking to the bottom of the tank.
Leafy sea dragons float for a vital reason: to blend in with seaweed and avoid becoming prey. Their sinking to the bottom was a clear sign that something was terribly wrong. It was later discovered that all three suffered from the same issue—a swim bladder that had never developed. This organ is crucial for buoyancy, and without it, the sea dragons couldn’t stay afloat.
In a brilliant solution, the vet fashioned floaties. He used black neoprene rings, a material known for its buoyancy, comfort, and resistance to salt water. These rings were placed around the sea dragons' delicate midsections and sewn together. The solution worked. Once the fish were able to float, they started feeding and growing again.
4. The Stickleback C-Section
In sticklebacks, the females release their eggs, leaving hopeful males to fertilize them. There's no romance or pregnancy involved in their typical reproduction. However, in the 1950s, a pregnant stickleback was discovered in Scotland. No further research was done at the time, but in 2016, scientists returned to Scotland and found another pregnant stickleback. Sadly, the fish was dying, so it was humanely euthanized, and the eggs were extracted through a C-section.
While there are only three known cases of egg-laying fish becoming pregnant, this was the first time the embryos survived. They were hatched in a lab and grew into healthy adults.
But how did a fish species that doesn’t carry young in the traditional way end up with healthy embryos in her belly?
DNA analysis revealed that the female didn't clone herself, as the babies had two genetic parents. It’s likely that the stickleback swam through a cloud of sperm and fertilized her eggs internally, through her egg tube.
In addition to being an extraordinary evolutionary event, the mother’s body had also stepped in to fulfill a crucial male role. Typically, male sticklebacks fan the eggs to ensure healthy development. In this case, the C-section fry were normal, suggesting that an unknown internal process had replaced the father's fanning behavior.
3. The Abandoned Shark
In 2012, a wildlife sanctuary near Melbourne, Australia was shut down. The operator, who was meant to protect a species of giant earthworm, was caught running an illegal animal park.
One of the creatures that certainly wasn’t an earthworm was a great white shark. This massive predator was supposed to stay there temporarily while its proper home was being readied. However, when new owners took over the park, they decided to keep the shark.
When the park was closed due to regulatory issues, the animals were handed over to the RSPCA. The shark’s fate took a strange turn from here. Not only was it abandoned at the worm sanctuary, but somehow it ended up in a tank filled with formaldehyde, where the 4-meter-long (13 ft) great white was preserved.
The deserted park had an eerie vibe, but the shark tank was downright terrifying. The corpse of the great white, suspended motionless in the murky green water, gained fame on the internet when urban explorers filmed it and shared the footage on YouTube.
2. The Sandwich Ray
The Macduff Marine Aquarium in Aberdeenshire is home to a number of thornback rays. Toward the end of 2018, the staff decided to clean one of the tanks, which contained ray eggs, also known as mermaid’s purses. As the babies had all hatched, the cases needed to be removed.
However, when an employee attempted to push the air out of one of the purses, it resisted. Upon peeling back a side, the worker was startled to discover an unhatched ray trapped inside. Since the egg case was damaged and the ray remained in its embryonic stage, a new surrogate shell had to be sourced.
The solution was as simple as it was unexpected—a sandwich bag. The ray comfortably incubated inside the plastic for two months before eventually 'hatching.' When it was time, the staff decided the ray was ready to leave the bag. It was removed and placed with 10 other rays, where it thrived, unaffected by its odd start.
1. Robot Guppies
The Trinidadian guppy has an unusual trait when it comes to its eyes. Normally silver, the eyes turn black in an instant when the fish becomes angry. Intrigued by this, researchers decided to craft robot guppies to determine whether this change was intentional and what it might signify among the fish.
In 2018, researchers took a deceased guppy and created silicone replicas of it. The lifelike copies, featuring either silver or black eyes, were placed near food and made to move with the help of a small motor. The resulting social dynamics revealed that the black eyes held a clear meaning in the guppy world.
Smaller guppies approached the food when the robot had silver eyes. However, when the eyes turned dark, it signaled what researchers described as 'honest aggression'—a clear indication that the guppy was ready to fight. It also conveyed that the guppy was protecting a valuable resource.
When the real guppies grew larger, they attacked the robot. This behavior was a way to claim the resource and intimidate a smaller fish bold enough to exhibit that look. The exact mechanism behind how guppies cause their eyes to turn black remains a mystery.
