Understanding Fish Reproduction: Causes and Considerations for Unexpected Offspring

This guide covers everything from the initial discovery of baby fish to their care and feeding. Equip yourself with knowledge to ensure these tiny surprises grow into healthy adults.

Article photo showing a bedroom with the text "Accidental Fish Babies"
It's inevitable that your fish at some stage in their life will breed - just be prepared!

The morning sun peeked through the curtains, casting shimmering patterns on my room's walls. As I groggily rubbed my eyes and adjusted to the light, I made my way to my favourite part of the room – the fish tank. It was my morning ritual: a cup of English Tea in one hand, and a peaceful few minutes watching my finned friends start their day.

But this morning was different.

As I leaned in, I noticed something unusual. Tiny, almost imperceptible shadows darted around the bottom of the tank. Squinting to get a better look, my jaw dropped in disbelief. There they were, multiple minuscule fish, fluttering their delicate fins and exploring this vast new world. My fish had pulled a sneaky one on me - they had bred overnight!

The wonder of life had unfolded right under my nose. It was a sight to behold, a surprise that added an extra dose of magic to my morning. The big fish continued with their usual business, seemingly unaware of the new additions. But I, their ever-observant caretaker, was in for the most delightful shock of my fish-keeping journey.

Photo of an aquarium with baby fry
So I bit the bullet and ended up purchasing a completely separate tank just for the babies... I'd guess around 30 babies were rescued and are all doing amazingly!

As the days turned into weeks, I embarked on a quest of discovery: learning the ins and outs of accidental fish breeding, from why it happens to how to best care for the new arrivals. So, fellow aquarists, if you've ever been curious about the unexpected surprises your fish tank might have in store, dive in with me as we explore this underwater adventure!

Quick Guide to Accidental Fish Breeding

Topic Key Points
Why did my fish give birth? - Water quality and temperature can influence breeding.
Fish eating their babies - Adult fish may consume fry; it's nature. Decide on intervention or let nature take its course.
Saving babies from being eaten 1. Separate them in a different tank or space.
2. Use breeding nets within the existing tank.
3. Scoop fry into safety using containers like old fish food tubs.
Feeding baby tropical fish 1. Crumble the same flakes used for adults into a powder.
2. Feed twice daily, but don't overfeed.
Breeding net setup 1. Avoid heavy gravel; it can weigh down the net.
2. Add small fake plants for comfort and hiding.
Releasing the babies 1. Release size depends on breed; 1cm for platies and mollies.
2. Slowly introduce them to the main tank.
Easy-breeding fish 1. Platies: Vibrant colors, live-bearers, breeds once a month.
2. Mollys: Elegant swimmers, also live-bearers, might require slightly brackish water for optimal breeding.

Why did my fish give birth?

Well, well, well, what have we here? A surprise fishy fiesta in your tank? You must've blinked, and voilà! – a handful of extra finned friends swimming about, causing you to scratch your head and wonder, "When did this little party start?"

Now, let’s get something straight: Fish aren’t exactly the type to send out baby shower invites. Nope, they’re more the spontaneous, "let’s have a bash!" kind of folks, especially when the mood is right. And by mood, I mean the water quality. Think of it as the champagne of the fish world; when it’s top-quality, everyone's feeling bubbly!

Your fish, bless them, just can’t help themselves. If the water's clean and crisp, they're thinking, "This feels just like a tropical holiday! Let's make it even merrier!" Moreover, crank up that water temperature a notch, and you might as well have lit some fishy candles. Warmer waters can make some species think, "Ah, the perfect setting for a family!"

In essence, if you've got boys and girls sharing the tank and they're floating around in some top-tier H2O, you've essentially set the stage for a fishy rendition of a Shakespearean romance – just with fewer monologues and more bubbles. So, next time you see those baby fry darting about, give yourself a pat on the back. You've unintentionally thrown the best underwater party in town! 🐟🎉

Will fish eat their babies if I don't rescue them?

Hold onto your fish nets, my dear aquatic aficionado! We're diving deep into the not-so-talked-about soap opera that unfolds in many an aquarium. Have you ever watched a nature documentary and thought, "Oh blimey, nature is harsh!"? Well, your fish tank can sometimes be a mini version of that!

Now, as much as we love our finned friends for their vibrant colours and playful antics, it’s time for a bit of fishy truth: many fish have, let’s say, a gourmet penchant for their own offspring. Shocked? Well, it's a fish-eat-fish world down there. Quite literally! Many species view those tiny, fresh-out-the-egg fry as tasty titbits, a quick snack if you will. Not the most parental instinct, right?

So, if you're picturing your aquarium as a haven where every fry grows up to tell tales of its adventurous youth, you might need to intervene. If you've got a heart of gold and wish to give these little ones a fighting chance, consider setting up a separate "nursery" tank or using breeding boxes within your existing tank. These boxes provide a safe space for the fry, away from the voracious appetites of their would-be predators.

On the other hand, if you're leaning towards letting nature take its mysterious and sometimes merciless course, that's entirely your prerogative. The circle of life does play out in all environments, after all. But one thing's for sure, whether you're playing lifeguard or spectator, the drama and dynamism of the aquatic world will never cease to amaze.

How do I save my babies from being eaten?

Photo of a breeding net stuck to the inside of an aquarium
If you're concerned that your fish will start to breed always have an aquarium Breeding Net to hand. They stick (with sucker pads) to the inside of your tank.

Indeed, the underwater world can be a tad more treacherous than one might think. But fear not! With some foresight and a bit of ingenuity, you can make sure those little swimmers get to grow up and tell tales of their great escape. Here's how:

Separate, Separate, Separate!

  • The number one rule when you've got baby fish in a tank with potential snacks? Put some distance between them. A separate tank, sometimes referred to as a 'nursery' or 'fry tank', is your best bet. It ensures the young ones can grow safely, without the constant threat of becoming someone's dinner.

Invest in a Breeding Net:

  • If a whole new tank sounds like too big a commitment (or if you’re tight on space), then a breeding net is your new best friend. This ingenious creation attaches inside your existing fish tank and acts as a protective sanctuary for the fry. Think of it as a playpen in the vast playground of your aquarium. Safe and secure!

Master the Art of the Swift Scoop:

  • Spot a baby fish out and about? Time to swing into action! Using a small container, like those old fish food plastic tubs, is perfect for this rescue mission. Gently scoop up the fry and transport them to the safety of the breeding net. Trust me, with a bit of practice, you'll become the superhero of swift scoops in no time!

And there you have it, folks! With these tips up your sleeve, you're well on your way to ensuring the next generation of fish in your tank have a fighting chance.

What do I feed my new Baby Tropical Fish?

Feeding time! One of the most exciting times in the fishy world, especially when you've got eager little mouths waiting. Baby tropical fish, or fry as we often call them, have specific dietary needs, and ensuring they get the right nutrition is crucial for their growth and well-being.

Stick to What You Know, but with a Twist:

  • You don’t have to dash out and get a whole new range of food just for the fry. Remember those flakes you've been using for the adults? They're perfect! But here's the trick: crumble them up into a fine powder. This makes it easier for the fry to consume and digest. It's all about size-appropriateness. Those little gills and mouths can only handle so much!

Consistency is Key:

  • With baby fish, it's not just about what you feed them, but also how often. These little ones have a rapid metabolism and require frequent feeding to support their growth. So, twice a day is the sweet spot. Regular feeding ensures they're getting the nutrients they need to grow strong and healthy.

Remember, while feeding is a delightful experience, it's essential not to overfeed. Any excess food can decay, compromising the water quality, which isn’t ideal for your fish – big or small. So, sprinkle in that crumbled flake powder, watch the feeding frenzy, and bask in the joy of nurturing the next generation of finned wonders in your tank! 🐠🍽️

Do I need to add gravel or plants to the breeding net?

Photo of a plastic aquarium breeding box with artificial plants inside
Only add lightweight plants (artificial is fine) to your breeding net/box. This prevents the box sinking and potentially allowing adult fish to feast on your new babies! 

Ah, the interior decorating of the fish world! Now, while a breeding net isn't exactly a sprawling fish mansion, it doesn’t mean we can't spruce it up a bit for our little residents.

Gravel - To Add or Not to Add?

  • Short answer: best to skip it. Gravel, especially the heavier types, can be a tad too weighty for breeding nets. And trust me, you don’t want to wake up to find your net has sunk, setting those little ones free prematurely. Even worse, imagine the horror of discovering bigger fish having a surprise snack party inside the net! So, as tempting as it might be to add that aesthetic touch with gravel, it's a risk better not taken.

Plants - A Tiny Touch of Comfort:

  • Now, here's where you can get creative. Small fake plants are a brilliant addition to the breeding net. Not only do they add a touch of greenery and beauty, but they also serve a functional purpose. Little fish adore hidey-holes! Providing them with small plants allows them to tuck away and feel safe, and that sense of security can be crucial for their well-being. So, while they’re not strictly necessary, adding a few faux plants is like giving your fry a mini safe haven.

To sum up, when setting up your breeding net, think safety first, followed closely by comfort. Those little ones might not be in there for long, but making their short stay pleasant is well worth the effort! 🌱🐟

When is the best time to release the babies?

Oh, the joyous day when our finned babies are ready to explore the vast waters of the main tank! But much like sending kids off to school for the first time, you want to be sure they're ready and well-prepared. So, when exactly is that?

Size Matters:

  • The size of the fry is often a good indicator of their readiness. For certain breeds like platies and mollies, the golden benchmark is when they've grown to at least 1cm in length. At this size, they are not just physically stronger, but they’re also less tempting for the larger fish in the tank. Essentially, they're less of a snack and more of a fellow swimmer.

Slow and Steady Does It:

  • Now, here's a crucial bit. While your babies might have reached the desired size, remember: the big tank can be a tad overwhelming for them! It’s a whole new world compared to the cosy breeding net. So, don't just drop them in. Instead, gently and slowly introduce them, allowing them to acclimatize to their new environment. Give them time to feel out the spaces, recognize potential hiding spots, and get a sense of the tank's residents. The last thing we want is for them to be scared out of their wits on their first day out!

In the grand scheme of fish-keeping, releasing the babies is like a graduation ceremony. You’ve nurtured them, provided a safe haven, and now, they're ready to join the broader world of the aquarium. Here's to their next big adventure! 🎓🐠🌊

What Fish Breed Super Easily?

Some fish are just natural-born breeders, and if you're hoping for a mini baby boom in your aquarium, certain species are more likely to deliver. Let's dive into two of the most prolific breeders that have earned a reputation for being quite the romantics!


  • The Colourful Characters: Platies, with their vibrant hues and vivacious personalities, are a favourite amongst aquarists, especially beginners. They come in a variety of colours, from fiery reds to sun-kissed yellows, making them a visually delightful addition to any tank.
  • Breeding Behaviour: One fascinating fact about platies? They're live-bearers! This means that instead of laying eggs, they give birth to live, free-swimming fry. A female platy can give birth to a brood every month, sometimes comprising dozens of little ones. So, if you’ve got a mix of males and females, brace yourself for a bustling nursery!
  • Care Tip: To ensure the best conditions for breeding, maintain a clean tank, stable water parameters, and offer a balanced diet.


  • The Graceful Swimmers: Mollies, with their elegant, elongated bodies and diverse palette of colours, bring a touch of class to any aquarium setup. Available in shades ranging from pure black to gleaming gold, Mollies are undeniably eye-catching.
  • Breeding Behaviour: Just like the Platies, Mollies are also live-bearers. Females can produce a batch of fry every month or so, and each batch can contain anywhere from 20 to 100 babies! It’s almost like having a mini aquatic conveyor belt of cuteness.
  • Care Tip: Mollies thrive in slightly brackish water. If you’re looking to encourage breeding, consider adding a touch of aquarium salt to their environment. Remember, though, that consistency is key. Sudden changes can stress your fish.

In essence, if you’re aiming to have a lively, ever-evolving fish tank with a constant influx of baby fish, both Platies and Mollies are fabulous choices. Their live-bearing nature ensures that there's always some action, and before you know it, your aquarium will be a bustling, vibrant community of fins and colours! 🐟🌈🍼