Fish tanks are tranquil until scientists want answers and drunk people want some fun. Then the fish stories start to get interesting . . . and more than a little weird.

Beyond the laboratory and fish-related emergency room visits, some of the best tales come from public aquariums. From lifesaving firsts to the mysterious case of a shark abandoned at a worm farm, no fishbowl will ever look the same again.

10 Infectious Fish Pedicures

A trendy way to exfoliate feet is to get a fish pedicure. Clients soak their feet in a container full of tiny fish that consume dead skin cells.

In 2018, a woman in New York allowed the fish, called Garra rufa, to feast on her toes. Months later, her toenails fractured. The bottom layer could be seen underneath the top.

Since it was painless, she did not visit a doctor for six months. Ultimately, she was diagnosed with onychomadesis. This condition occurs when something stops nails from growing and, eventually, they fall off. When all other causes of onychomadesis were ruled out (injury or a family history of nail disease), the woman became the first case linked to a fish pedicure.^[1]

In the past, Garra fish had tested positive for several bacteria that cause skin and tissue infections. Hygiene is another problem. Since the fish are in the tubs, the containers cannot be properly cleaned between customers. Sanitary risks include individuals with foot diseases who use the tub before other clients.

9 Oldest Fish In Captivity

In 2018, an Australian lungfish in San Francisco celebrated her 80th year at the California Academy of Sciences’ Steinhart Aquarium. Her age is closer to 90 as she arrived as an adult in 1938. Named Methuselah, she measures 1.2 meters (4 ft) long.

The oldest fish in captivity loves figs and prawns, belly rubs, and certain volunteers. Methuselah also prefers her own tank. When caretakers placed her in a larger aquarium with two younger lungfish, she insisted on hovering upside down until they moved her back.

Genetics play a role in her long life, but the species is extraordinary in other ways. Lungfish, which are primitive and go back 400 million years, use a swim bladder to float and breathe air. Some even walk over the ground to search for a new pond.

Methuselah seems happy to aim for a century. According to her caretakers, she eats like a pig and loves human interaction. For this reason, the aquarium’s coddled group of lungfish are often called “underwater puppies.”^[2]

8 Fish Have Personalities

Scientists tackled a tricky question in 2015. Wondering if fish had personalities, they decided to create a horror show. They scared guppies with a fake heron beak plunging into the water. On another occasion, they used “Big Al.” He was a carnivorous fish called a cichlid which would suddenly appear on the other side of the glass.

When a guppy was moved to this scare tank, the only shelter was a small plastic cover. After getting the holy sin frightened out of it, the single fish would be returned to a well-protected tank full of other guppies. After three days, it went back to the scare tank to endure five minutes of terror. This continued for a month.

After putting each of the 105 guppies through this experiment, scientists concluded that the fish had personalities. All reacted in a unique way. It was not accidental. The guppies repeated their chosen behaviors (hiding, fleeing, freezing) during the follow-up encounters with the heron and cichlid every three days.^[3]

7 Catfish Drinking Game

In 2016, a drunk man arrived in the emergency room with a bizarre injury. That evening, the unnamed 28-year-old had partied with friends in Rotterdam in the Netherlands. They had decided it would be a good idea to swallow live fish.

Several goldfish were taken from a home aquarium and gulped down without a problem. Then someone suggested another tank occupant—a small catfish. However, it was a Corydoras aeneus, a toxic creature with spines. When threatened, these catfish stiffen their venom-filled needles to avoid getting eaten.

Needless to say, the spiky creature got stuck in the man’s throat. Choking, he threw up blood and beer—but no fish. His drunk friends applied the Heimlich maneuver incorrectly. The man tried to wash the fish down with beer, ice cream, and honey. Finally, after waiting several hours, he went to the hospital.^[4]

Delicate surgery ultimately removed the dead catfish. It was preserved in the Rotterdam Natural History Museum, joining a collection that highlights dramatic encounters between humans and animals.

6 Wrasse Recognize Themselves

There is a simple test for self-awareness. A mirror shows the subject an artificial mark on their body. Any related reaction, like rubbing the spot, suggests an awareness that the image represents their real body. Animals that have passed include dolphins, chimpanzees, elephants, pigeons, and crows.

In 2018, researchers wanted a self-aware fish. They picked the cleaner wrasse. One ability made them the perfect candidate. Wrasse feed on parasites. They have evolved to notice unusual spots on other fish.

When 10 wrasse were isolated in individual mirrored tanks, things got interesting. At first, they mistook their reflections for rivals and fought with themselves. However, within days, they performed “friendly dancing” in front of the mirrors.^[5]

Wrasse are solitary and do not dance for other fish. Although hard to prove, they could have been dancing to see themselves move. When colored gel was applied to their heads (only noticeable in the mirror), seven wrasse spent more time with their reflections or rubbing their heads against things in the tank.

5 Fish Floaties

Leafy sea dragons resemble seahorses that ate too much plant fertilizer. The entire fish is covered with leaflike fronds.

In 2018, the Florida Aquarium in Tampa acquired three young sea dragons. While observing the Australian fish, the aquarium’s vet noticed something distressing. They ate badly and kept sinking to the bottom of the tank.

Leafy sea dragons float for a reason—to look like seaweed and not food. For them to hit the dirt meant something was seriously wrong. Surprisingly, it was discovered that all three suffered from the same condition—a swim bladder that never developed. The organ is responsible for buoyancy, and without it, the trio could not get off the floor.

In a genius move, the vet created floaties. He used black rings made of neoprene, a buoyant material that was both comfortable and resistant to salt water. The rings were looped around the sea dragons’ fragile midsections and sewn together at the ends. It worked. Once the fish found themselves floating, they started feeding and growing again.^[6]

4 The Stickleback C-Section

Stickleback females spray eggs for hopeful dads to fertilize. There is no hanky-panky or pregnancy with this species. In the 1950s, a pregnant stickleback was found in Scotland. No investigation was done. But in 2016, researchers trawled Scotland for more and found a heavily pregnant stickleback. Since she was dying, the fish was humanely destroyed and the eggs removed via C-section.

Although three cases are known (where egg-laying fish got pregnant), this was the only time that the embryos survived. They hatched in the laboratory and became healthy adults.

But how did a member of a species that doesn’t get pregnant carry healthy young in her belly?

DNA tests showed that she did not clone herself because the babies had two parents. The stickleback likely swam through a sperm cloud and was fertilized through her egg tube.

Beyond being a major evolutionary leap, the mother’s body also aced a crucial male role. To stimulate a healthy development, stickleback dads fan the eggs. The C-section fry were normal, meaning a mysterious internal process had replaced the father’s fanning.^[7]

3 Robot Guppies

The Trinidadian guppy does something weird with its eyes. Although the eyes are usually silver, anger turns them black within seconds. As researchers are curious creatures who go the extra mile, they decided to create robot guppies to find out if the change was voluntary and what it communicated within this fishy population.

In 2018, they took a dead specimen and made silicone replicas. The incredibly realistic fakes had either silver or black eyes. They were positioned over food and given lifelike movements thanks to a small motor. The social dynamics that followed showed that black eyes had a very specific meaning.

Smaller guppies approached the food when the robot had silver eyes. However, a dark look communicated what researchers called “honest aggression”—the guppy’s absolute readiness to fight. It also meant that the guppy was guarding a worthy resource.

When the real guppies were bigger, they beat up the robot. This was to loot the resource and thrash a smaller fish that dared to use the look. It remains unknown how guppies flood their eyes with black.^[8]

2 The Sandwich Ray

Macduff Marine Aquarium in Aberdeenshire is home to several thornback rays. Late in 2018, staff decided to clean one of the tanks. It was filled with ray eggs, known as a mermaid’s purse. In this case, they had to be removed as all the babies had hatched and the cases were empty.

However, when an employee tried to push the air out of one purse, it would not give. He peeled back one side and was surprised to find an unhatched ray. The unlucky creature had been trapped inside its egg. Since the case was destroyed and the ray was still an embryo, a surrogate shell had to be found.^[9]

The solution was as simple as it was unusual—a sandwich bag. The ray happily incubated inside the plastic for two months and eventually “hatched.” The day came when staff decided that it was ready to leave the bag. The baby thornback was removed and placed with 10 others where it thrived, seemingly unaffected by its peculiar past.

1 The Abandoned Shark

In 2012, a wildlife sanctuary was closed down outside of Melbourne, Australia. The operator was supposed to preserve a species of giant earthworm but was caught running an illegal animal park.

One of the creatures that was definitely not an earthworm was a great white shark. The enormous predator was supposed to stay there temporarily while its real home was being prepared elsewhere. However, when new owners took over the park, they kept the shark.^[10]

When the park was closed due to irregularities, the animals were handed over to the RSPCA. At this point, the shark’s story gets muddy. Not only was it left behind at the worm sanctuary, but it also somehow ended up in a tank of formaldehyde. This preserved the 4-meter-long (13 ft) great white.

The empty park could be considered spooky, but the shark tank was downright haunting. The corpse, hanging motionless in green water, recently became an Internet sensation after urban explorers encountered the beast and posted the video to YouTube.

Fish have been a part of the human diet for centuries. We have learned more about the risks and benefits of eating fish over time. We have also become quite fond of the taste and texture of fish. (Well…not our vegetarian and vegan friends.) Eating fish offers nutrients that aid in reducing the risk of death from heart disease. It also lowers the risk for other health conditions such as stroke. We even understand the role these nutrients play in the brain development of infants.

But…too much of a good thing is bad. Moderation is key.

Fish contains mercury and other contaminants. (Think about the polluted oceans.) Overconsumption of fish increases your level of mercury within the body. This is dangerous for pregnant and nursing women and their babies. The U.S. Department of Agriculture has created guidelines and interactive online tools to inform the public on safe fish consumption.

Yet, depending on your culture, traditions, and where you are in the world can determine the part of the fish you eat. In the U.S., many eat fish fillets and consider the remaining parts of the fish “undesirable.” Even though not everyone eats fish every day of the week, we all have some sort of encounter with a fish product every day. With the demand for fish increasing all over the world, fishermen and scientists are determined to find ways to repurpose fish waste or fish by-products.

Let’s dive in…

Related: 10 Products Which Were Invented In Unusual Ways

10 Biodiesel

Fossil fuels are a limited source. They are nonrenewable. Once they are gone, we cannot create more. It is not ideal to wait millions of years in the hope that more will form. But there is no need for a lengthy science lesson. In short, scientists have already begun searching for other sources of sustainable energy. From wind-powered turbines to solar panels to electric-powered cars, the search continues.

Someone had a bright idea to create an alternative fuel source. A less costly but energy-efficient source using fish by-products. Fish processing units produce billions of tons of fish waste every year. The waste or discarded fish parts such as bones, skin, and even fish heads are usually dumped back into the ocean—adding to our already polluted oceans. Eco-friendly biodiesel is created when the fish by-products or waste are pressed, and the fish oil is then extracted. The fish oil is the base for the biofuel, but other compounds are added before it is ready to be used by your car’s engine or even a plane.^[1]

9 Cosmetics

Ever thought about using fish skin on your face? We all want to look our best, don’t we? It makes us feel even better when we can use a beneficial product that makes a positive impact on our environment, right? In the beauty and cosmetic industry, collagen is well-known for its wrinkle-reducing properties and ability to improve skin health.

Marine collagen, or collagen derived from fish skin, has the same benefits as mammalian collagen (LINK 6). It can be used as a moisturizer for the skin to fight against aging. Maybe it will be your new favorite product to add to your daily routine. Other cosmetic products derived from fish by-products are nail polish remover, hair styling gel, and some makeup applications—the fish by-product is the base.^[2]

8 Gelatin

Can you imagine having strawberry and fish gelatin cups as a dessert? Or cranberry, vodka, and fish gelatin shots to unwind after a long week? Desserts are a sweet spot for me. And I can say that I have never considered having fish for dessert. Gelatin is usually made from cow and pig by-products, but it is also made from…you guessed it…fish. Though it may not be able to completely replace mammal-based gelatin, it does provide another option for those with religious concerns.

However, there are some different chemical properties of mammalian gelatin and fish gelatin. For example, gelatin from fish has a lower gelling point—the temperature at which the substance begins to solidify and form into a gel. Scientists performed a study and found that fish gelatin would be great for frozen desserts like ice cream. Just like mammalian-based gelatin, fish gelatin can also be used as a food additive.^[3]

7 Animal Food

Fish by-products are found in animal feed and pet food. This one may not be much of a surprise. But it is one that those without pets or those who are not familiar with livestock may overlook. Animals and humans both benefit from adding fish to their diet. The protein-rich fish by-products help with the growth and development of our beloved pets and livestock.

Also, the rise of animal lovers wanting to give their furry friends high-protein-rich food and treats has opened the market for new sources of meat. Fish skin is notably high in protein while low in ash, so it is an obvious choice to use in the manufacture of animal feed and pet food. With over $42 billion spent by U.S. consumers on pet food in 2020, with Millennials more focused on organic products, the need for safe and sustainable sources is obvious. And this is where fish by-products can really help. ^[4]

6 Food Packaging

The most frustrating thing about enjoying a snack during a hangry moment is trying to open the package. All frustrations aside. Great packaging for a product usually means that the product’s freshness and taste are preserved. It also improves the shelf life of the product.

To create ideal food packaging, companies usually use plastic films. But fish skin can be used to create a thin film that is biodegradable and an effective barrier. Gelatin films made from fish skins are great barriers or protectors against oxygen and oil. While it may sound unappetizing, it may help reduce our reliance on plastic-based packaging. As long as this fishy cling film is easier to get off of the roll without folding in on itself, we’re set!^[5]

5 Pharmaceutical and Medical

There are various ways fish by-products are used in the pharmaceutical and medical industries. Actual fish oil—in its liquid form—can be taken as a dietary supplement as can as marine collagen. Nutritional supplements have many forms, like liquid, powder, and capsules. For example, fish gelatin can be used to coat capsules for medicine or even create those gummy vitamins that are popular with children…and adults.

Even with a fish-rich diet, you still may not be getting all the fatty acids you need from your diet. Fish-coated supplements are a way that you can absorb those needed lipids to help lower your risk for cardiovascular disease, hypertension, and autoimmune and inflammatory diseases.

Some studies have also revealed that fish by-products can play a role in such medical products as artificial human skin, fine-grade absorbable sutures, and products to arrest bleeding during certain microsurgeries.^[6]

4 Clothing and Accessories

Fish are always in style—from the vibrant colors to mermaid tail flare to fishnet stockings. Whether inspirationally or literally, using fish in your wardrobe is not for those lacking a fashion sense.

In the past, Nordic countries used fish skins to make shoes and pants. They were even used to create an accessory like a bag or sack. Imagine a pair of leather fish skin boots with a fin-tastic matching bag. Today cowboy boots made with fish skin leather are thought to be luxurious even in the United States. One designer is even making sunglasses from salmon skin.^[7]

3 Household Items

Take a moment and look around your home or wherever you are right now. With minimal effort, you can find at least three products that use fish by-products. Ok…maybe it’s not the exact product in your home, but there are similar products in existence.

Fish waste is used to make soaps, candles, lubricants, rubber, detergents, printing ink, paint, varnishes, and glue. Fish glue is commonly used to bind wood, paper, or leather, and it is known to have a low setting time. Candles use the oils created from fish by-products. How many more functional products can be created from repurposed fish waste?^[8]

2 Photography and Electronics

Film photography seems to be a thing of the past. However, new technology is relevant and prevalent. To be more eco-friendly, scientists came up with a biodegradable film for photography and some electronic devices.

Thin and transparent films are made from fish scales for flat electronics such as logo display lighting and flat-panel displays to help with flexibility and a green or environmentally friendly approach. Similar to the benefits of using fish by-products as food packaging, films treated with fish gelatin increase the storability of photos—the ones you can hold in your hands, not digital.^[9]

1 Fertilizer

Have a green thumb? The common use of fish by-products is as a fertilizer. Often fish by-products are called fish offal. It is a term to describe all the discarded portions of the fish, including the eyes, head, heart, swim bladder, tail, scales, eggs, and milt. Using fish offal fertilizer is n everyday practice in organic agriculture, focusing on providing quality food from the environment while maintaining soil fertility. The fish offal is ideal fertilizer due to its nutrient-rich composition, low cost, and rapid decomposition.

There are more ways fish offal is used, but they did not make the top ten list. For example, isinglass is formed from dried fish bladder and sometimes used to clarify beer, wine, and vinegar. Another example is dried salmon skins, which are now being advertised in the mainstream as a healthy snack. There are many recipes using fish offal that offer a slight nudge toward eating nose to fin.

Scientists and fishermen are still looking for creative and beneficial ways to use the massive amount of fish waste created every year. But we can help too. How? Brainstorm. What way could I practically use fish oil? Where can we decrease the exploitation of fish? Bounce ideas off a friend. Do not shy away from sharing your thoughts. Maybe your next idea could be the one the world needs.^[10]