Beautiful but Broken: The Ethics of Hybrid Fish

The topic of hybrids in the world of aquaristics has divided people for years like few others.

Some are fascinated by them – because they are original, because they are different, because “wow, this has never been seen before.”

Others, however, hold their heads, talking about ethics, fish health, and destroying genetic purity.

To be honest, it’s hard to blame them – the matter is not black and white. But let’s start from the beginning: what exactly are these hybrids and where does all the fuss come from?

Hybrids – what are they anyway?

Before we start breaking everything down, it’s worth explaining one thing: what exactly is a “species”? In short – it is a group of organisms that can reproduce with each other and have fertile offspring.

When we combine two different species (or subspecies, breeds, etc.), a hybrid is formed. Something in between.

Such a crossbreed can arise naturally – for example, when the environment changes and two species start to “overlap.” Or artificially – in an aquarium, when a breeder decides to experiment.

In nature, hybridization is rather a side effect of changes caused by humans, e.g. river transformations or introduction of foreign species.

Scientists – Olden and co-authors – in their 2004 study showed that environmental changes – such as new water dams or presence of foreign species – can cause uncontrolled fish crossbreeds in North American rivers.

But in aquaristics? The matter gets even more interesting. Because here we deal with closely related species, which not only can reproduce, but their offspring can be… well, better than the parents.

Bigger, stronger, more resistant. This phenomenon is called heterosis. The problem is that such a super-fish can “push out” the original species from the ecosystem. And that ceases to be an innocent game with genetics.

Imagine that you create a hybrid that eventually displaces both original species. That is no longer a simple crossbreed – it’s something like a fish Frankenstein.

And to be clear – it’s not a situation like “let’s cross a poodle with a labrador.” Because poodles and labradors are still the same species. It would be more like trying to combine a poodle with… a fox. Something that looks possible on paper, but in practice raises many questions.

Alright, but why do it at all?

Some will say: for appearance. Others: out of curiosity. And yet others – out of concern for species survival.

Because let’s not forget that aquaristics is also a form of conservation. Seriously. There are so-called conservation colonies – breeders reproduce fish from specific locations so that they do not disappear from the face of the earth. They try to preserve genetic purity, especially if a species is endangered in the wild.

On the other hand… most of us don’t keep fish in order to release them later into the Amazon. We buy them in stores, sometimes not even knowing where they come from.

And if there is no genetic documentation, then – let’s be honest – do these fish still have anything to do with the wild nature at all?

It’s hard to say.

DNA – a puzzle that can’t be predicted so easily

If we could read the full DNA sequence of every fish, we would have access to absolutely everything – color, shape, instincts, behaviors… even brain structure. But nature doesn’t work like an Ikea catalog. A hybrid doesn’t always inherit everything from both parents in equal proportions.

An example? A hybrid of Tiger Shovel Nose catfish and Red Tailed Cat – it can grow like crazy, even faster than the parents. In the right crossbreeding combination, you get a “superfish.”

But if you do it the other way around, suddenly you have sickly, weak individuals with no future. It’s probably about growth genes – inherited only from one parent. The hybrid might not have it at all… or get two copies as a package. Kind of like a lottery.

Where do new species even come from?

Sometimes a hybrid is just a transitional stage. In nature, new species appear when a group of fish is separated – for example by a change in a river’s course.

In one part – rushing water and predators, in the other – a calm lake and a different diet. After several dozen generations, these fish differ so much that it’s hard to say they are still the same species.

And what if they meet afterwards? They might crossbreed… but sometimes they “don’t understand each other” anymore.

And even though technically they can have offspring, it might not be viable. Or won’t be able to reproduce. And sometimes – against all odds – a hybrid is stronger than both parents and becomes a new player in the ecosystem.

But, unfortunately, it’s humans who more and more often artificially accelerate this process.

Hybrids in the environment – a threat or not?

If we talk about the natural environment – definitely yes. Especially if these hybrids end up in rivers or lakes.

A study from Mexico (López-Fernández et al., 2017) shows that swordtail and molly hybrids, introduced into local rivers, displace native species. They are stronger, more competitive, and can reproduce – exactly what we don’t want.

Examples of hybrids

Blood Parrot

Is there any fish more controversial than the parrot cichlid, aka Blood Parrot? Seriously, for almost 40 years it has caused extreme reactions – some love it, others would most gladly ban its sale. And, I admit, I am closer to the second group.

It’s not that it’s a hybrid. That could still be tolerated. But the problem is that it is a fish artificially “glued” together with serious structural defects. When it appeared on the market, its little mouth was so deformed that it barely opened.

Feeding such fish was almost a miracle, and malnutrition was practically the norm. On top of that, there were problems with the swim bladder, gills, and even internal organs.

Some of these deformities are the result of crossbreeding itself, but the main culprit is genes responsible for the so-called “balloon” body shape.

Something that in theory was supposed to look “cute” in practice often means a suffering fish. And not only in the case of Blood Parrot — similar things are seen in balloon mollies, plecos, rainbows, gouramis… The list goes on.

There is quite a mess in aquarium literature, by the way. Some write that Blood Parrot is simply a balloon version of the Midas or Red Devil Cichlid. Others point to Severus, Red Head, or maybe even the Honduran Red Point Cichlid as “parents.”

It’s hard to say. In my opinion, under the name Blood Parrot hides a whole mix of various hybrids, depending on what someone managed to cross and sell at a given time.

And Jellybean Parrot? Probably an even more extreme version – a short-bodied zebra cichlid mixed with mutations and unlucky genes.

In the 90s these fish could cost a fortune. Today they are much cheaper and… a bit less deformed. Is this a sign that breeding has improved? Maybe. Or maybe simply those who had the worst genes already spread them, and now this is the “new normal.”

For me, they are still just heavily deformed Zebra Cichlids. And even if they really are hybrids, they are rather close relatives – e.g. with the Honduran Red Point Cichlid, which some don’t even treat as a separate species.

But honestly – it’s not about who was “mom” and who was “dad.” It’s about the fact that these fish are the result of deliberate selection of deformities.

And if we have a choice between a healthy fish and one whose spine is bent, jaw doesn’t close, organs are somewhere they shouldn’t be, and on top of that can’t normally communicate with others… What would you choose?

Some say there is no hard evidence that these deformities cause pain. Maybe there isn’t. But we also don’t have proof that the pain isn’t there. And since we don’t know, maybe it’s just better to be cautious and act with empathy.

Flowerhorn

The first time I saw a flowerhorn as a kid and… well, my jaw dropped. That hump on the head, intense colors, patterns like from some cosmic catalog. For a long time, I was convinced it was an exotic fish from the jungle, something rare and special.

Only later, as an adult, did it hit me that flowerhorn doesn’t exist in nature. It’s not some “strange species from the tropics,” but a product of crossing several cichlids from Central and South America. The effect of human creativity, or – depending on how you look at it – interference.

We know for sure that a large part of the genetic material comes from the Trimac Cichlid. The problem is that fish that don’t meet breeders’ expectations often end up for sale under false names. Or, worse, are released into the natural environment.

Sounds absurd? Yet it happened. In Lake Malili on Sulawesi – a place that is like the Holy Grail for biologists – Flowerhorns started reproducing. Studies from 2012 confirmed that this hybrid spreads quite effectively there.

The problem with such hybrids is that their DNA is more “flexible” than pure species. Because of this, it’s easier for them to adapt to new conditions. It’s a bit like playing genetic bingo, only with a higher chance of winning.

Discus, Guppies, Bettas

Discus? Here, too, it’s not simple. Most of those that end up in aquariums today are hybrids — and that’s not controversy, just a fact. Moreover, even some wild-caught individuals may already have mixed genes.

On top of that, scientists still don’t agree on how many discus species actually exist — five? Different studies say different things.

Furthermore, even the most diligent breeder can accidentally cross two fish that seem to be the same species, only to find out later that according to new classification… oops, actually not. And in regions where species overlap, natural crossbreeding happens by itself.

But in this case, we’re not talking about an ecological disaster — wild forms still persist, and evolution keeps working. In fact, all our knowledge about breeding discus was developed before we even distinguished their species.

And it is precisely from these “uncertain” crosses that all these beautiful varieties that amaze us today originated. An example? To create the leopard snakeskin, you have to cross Symphysodon tarzoo with Symphysodon aequifasciatus. And voilà.

The same applies to guppies and bettas — it’s hard to say today what their original forms were. And since scientists keep changing classifications and discovering new species, it becomes quite a labyrinth.

But one thing has to be admitted — they are colorful like a rainbow after a storm. Why? Because in hybrids, the genes responsible for colors are “scattered” in different parts of the DNA. In “pure” species, colors usually inherit at specific genome locations, so the effect is quite predictable. In hybrids — there is more chaos, and consequently, more diversity.

Arowana

The Asian arowana. Well, it’s possible it’s a hybrid too. But does that surprise anyone anymore? After all, these are no longer wild fish — they’re bred only for aquariums, far from their natural environment.

The problem starts when something goes wrong. For example — someone accidentally releases 15 thousand arowanas into the wild. Sounds like a joke, right? But it really happened.

The internet was flooded with photos of people boasting they ate this absurdly expensive fish, then complaining that they found… microchips inside. Yes, inside the fish.

Not all of them ended up on the frying pan, though. Some reached the river, regaining access to areas where the wild form Scleropages formosus once lived. And if researchers are right and there are more species — for example, four — then there’s a risk that the released fish were, for example, Scleropages aureus, or worse — hybrids.

And this, in turn, could mean one thing: local populations may have already ceased to exist. It’s hard to assess today — time will tell how far these changes have gone.

The dark side of hybrids

Let’s not beat around the bush — one of the most serious criticisms of breeding hybrid fish is the health problems that emerge over time. To put it bluntly: some of these fish simply suffer. Deformities, skeletal issues, difficulties feeding… It sounds harsh, but that’s the reality in many cases.

In a 2015 study by Zhou et al., they looked at so-called blood parrot cichlids and the results are not encouraging. Skull deformities, jaw problems, odd body posture — these are not things that should be normal. And it’s all because when creating these fish, the focus was solely on appearance, completely ignoring physiology.

Moreover, it’s not only scientists who notice this. According to the World Small Animal Veterinary Association (WSAVA, 2019), animal breeding — even ornamental — should consider their welfare. And if selection leads to suffering, it is simply unethical. Period.

Another topic that often comes up is fertility. Or rather, the lack of it. Many hybrids have reproductive problems, and some are completely sterile. Why? This is due to genetic conflicts between species — differences in chromosomes and such (Coyne & Orr, 2004).

Bartley and colleagues (2001) showed that hybrid fish often exhibit aneuploidy, sperm production disorders, poor gamete quality…

It sounds like lab jargon, but in practice it means one thing: these fish cannot reproduce effectively. Breeders therefore have to constantly create new individuals from scratch. Kind of like a factory.

But that’s not all. Hybrids can pose a real threat to wild populations. If accidentally released into the natural environment, so-called introgression can occur — meaning their genes infiltrate local species. And then it becomes a serious mess.

This has already happened. In the Amazon basin, where populations of Ancistrus catfish were studied (Chiachio et al., 2020), scientists began to have trouble recognizing who was who.

Hybrids introduced into the trade so mixed up the genetics that it was hard to clearly define species membership. For nature conservation and taxonomy, this is a nightmare.

And finally — a question many prefer not to ask: where is the limit? Do we really have to design fish just to make them prettier? For whose pleasure do they really exist?

According to many biologists and ethicists (such as Rollin, 1995), if an animal exists only to look good — even though it suffers — we treat it as an object. And that’s not just a biological problem, but a moral one. One that concerns all of us who keep aquariums.

Okay, but do hybrids have any advantages?

Yes, they do. And it would be dishonest to pretend otherwise. Hybrids are popular for a reason — and not just because it’s trendy.

First: appearance. Intense colors, unusual patterns, sometimes shapes you won’t find in nature. A flowerhorn with its characteristic hump is a true “wow factor” in the aquarium. It’s no wonder many aquarists simply enjoy looking at them.

Second — more choice. Thanks to hybridization, you can create very interesting compositions in a tank. For some, it’s even a form of art. Added to this is the fact that many hybrids are more disease-resistant and less sensitive to water parameter changes. That’s a huge plus, especially for beginners in the aquarium hobby.

Breeders often deliberately combine specific species to get fish with desired traits — whether temperament, ease of care, or appearance. As a result, forms well adapted to aquarium life arise. Sometimes even better than their wild counterparts.

It’s also worth mentioning that hybrids are usually bred in controlled conditions, so there’s no need to catch them in the wild. This reduces pressure on wild populations.

And by the way — the whole process gives breeders a chance to learn. Genetics, biology, behavior — it’s not just a game of crossing fish, but also deepening knowledge.

In short: if someone does it responsibly, thoughtfully, and with respect for the animals, hybrids can bring real benefits. Both for the fish and for people.

So how is it really with hybrids? Good or bad?

To be honest… it depends.

I’ve had more than one hybrid in my aquarium. And I’m not ashamed of that. But over time, I started asking myself questions — what’s more important: the appearance or the health of these fish? Their comfort? Do I really want creatures in my tank that barely breathe because someone thought it would look “prettier”?

Discus, mollies, bettas — many of them are no longer wild fish, but hybrids domesticated over generations. Maybe instead of pretending it’s still nature, we should start treating them as new species and make sure they are healthy, strong, and well adapted to life in an aquarium?

That should be the goal of breeding. And if you don’t know how crossing will affect the health or behavior of the fish — simply don’t breed them. This isn’t a game or an experiment.

Besides, sometimes you don’t even have a choice. Want to buy a Trimac or some Synodontus? Well — it will almost certainly be a hybrid. And the situation with fish from Lake Malawi? Even worse. There, hybrids have completely blurred the differences between species.

But what annoys me the most is the deliberate deforming of fish. Turning them into caricatures because they sell better that way. No, we shouldn’t support that. If a breeder can’t provide decent conditions for fish — don’t buy from them. We have thousands of other species to choose from.

And you know what? Many traits we value in hybrids — color, temperament, resilience — often occur in pure forms as well. Maybe just look around?

Unless it’s deformities that fascinate you. In that case… well, maybe it’s worth asking yourself some tough questions.

We’re not really sure what exactly fish feel — pain, stress, discomfort — but since we don’t know, we should be even more careful. With empathy. For me, intentions matter a lot.

I don’t need fish glowing like neon signs or twisted into unnatural shapes. I like natural tanks, as close as possible to what happens in nature.

And no, I’m not judging anyone who keeps hybrids.. But I encourage reflection. Think about what’s okay for you and what’s not. It’s your choice — just make sure it’s a conscious one.