Breeding

Caring for goldfish can be very rewarding. You set up their tank, make sure their water is just right , choose what food they eat, and watch your goldfish grow and play.

But there is something even more rewarding than looking after a goldfish you bought from the pet store. How about raising a goldfish all the way from birth to adulthood?

In this guide to baby goldfish, we look at how goldfish babies are born, how they grow, and – most importantly – how you should care for them.

How do goldfish have babies?

Before baby goldfish can be born, two sexually mature adult goldfish must mate.

Goldfish only mate at specific times and under specific conditions. For example, the temperature of the tank is important.

If you’re not sure how to encourage your goldfish to mate, or if they are ready, check out our guide to breeding goldfish to learn more.

Once your goldfish have successfully mated, the female goldfish will lay eggs. Then, the male goldfish will fertilize the eggs.

About 4 days later, the eggs that were successfully fertilized and survive – i.e. don’t get eaten by the adult goldfish or sucked into your filter! – will hatch.

Your goldfish babies have been born!

What do the babies look like?

Once your goldfish eggs hatch, you’ll need to look closely to find the tiny goldfish babies.

For the first 4 days or so they will be stuck to the leaves of your plants, so look carefully. Where you previously just saw eggs, you should now see tiny black baby goldfish with their yolk sacs attached.

After about 3 more days, your goldfish will be able to swim around freely.

What color are the babies and how does this change?

Newborn baby goldfish start out black.

As they grow, they develop a brown color, perhaps with hints of silver. Some areas of their body are almost see-through.

It can take up to two years for a goldfish to fully develop its color.

And even then, goldfish can continue to change color throughout their lives.

Baby goldfish growth rate

Of course, baby goldfish don’t stay so tiny and black in color for long.

One of the joys of breeding goldfish is that you get to see the babies grow and develop over time.

Once your baby goldfish reach the free-swimming stage, their bodies will be around 5mm long. They will have a very small stubby tail, pectoral fins (on their sides) and a fin on their back too.

Over the next week, your baby goldfish will grow by almost 40%. Their caudal fin (the tail fin) will develop a lot during this stage of growth.

The following week – the third week after hatching – your goldfish will continue to grow quickly. You’ll also notice their dorsal fin (the fin on their back) becoming more defined.

By the fourth week, the dorsal fin will be well developed.

By the fifth week, all of your fish’s fins will be well developed and they will have scales.

From week six onward, your fish is essentially “complete”. Like a miniature version of an adult goldfish. From now on, it’s all about growing in size and weight.

Caring for baby goldfish

Tank

To stop your adult fish from eating their own eggs, you should remove your goldfish eggs from your main tank as soon as they have been fertilized by the male.

Removing the eggs could be as simple as transferring your spawning mop, if you used one. Or you may have to gently siphon the eggs off things like plants and decorations.

Place the eggs into a small tank – perhaps 3 to 5 gallons in size (like this one) – with around six inches of water.

Add a small sponge filter to the tank. Don’t add a large, powerful box filter, as the babies will very likely get sucked inside!

Your baby goldfish should stay in smaller tanks – separate to the adult fish – until they meet two important conditions:

1. They are strong enough swimmers to not get sucked into the main tank’s filter
2. They are bigger than the adult fish’s mouths!

Only once these conditions are met should you add babies to an adult tank.

Temperature

We recommend maintaining a temperature between 70-75^oF (21-24^oC) in your baby goldfish tank. This temperature is warm enough to encourage rapid growth, but without being too hot for your fish.

It’s very important to avoid any sudden changes in temperature. A sudden drop to a cold temperature will stress your fish, which could cause them to get sick or even die.

Food

The first few days

For the few first days after hatching, you should not feed your baby goldfish at all.

While this might seem odd, it’s because the goldfish arrive well-prepared with their own packed lunchbox!

Baby goldfish hatch with a “yolk sac” attached to their bodies. This pouch contains all the food they need for the first few days.

The first month

Take some hard-boiled egg yolk and soak it in water. Give it a good shake, then add to your baby goldfish tank in small quantities.

You may also wish to try crushed brine shrimp and baby fish food.

Remove any food that is left uneaten so that it doesn’t pollute your tank.

The second month on

Your fish should now be able to eat the same foods you feed to your adult goldfish.

Just be sure to crush up the food if necessary. You need to make sure the pieces aren’t too big for the babies mouths!

Death

We should add that – no matter how well you care for the babies – you should be prepared for lots of them to die.

The reason that goldfish lay so many eggs, and that so many babies hatch, is that only a small percentage make it to adulthood. They need to have lots of babies to ensure that some survive.

If you manage to keep 20% or more of your baby goldfish alive to give away to other people, or to move to your adult tank, you’ve done very well.

What are baby goldfish called?

Throughout this article, we’ve referred to the little new members of your goldfish family as “babies”. However, this isn’t the technical term for baby goldfish.

When they first hatch from their eggs, baby goldfish are called larvae. They carry a yolk sac with them for food. This periods lasts for two to three days.

The baby goldfish then lose their yolk sacs and become capable of feeding themselves. Once they reach this stage, the babies are called Fry.

Once baby goldfish develop scales and have fully formed fins, they are known as juveniles. This phase lasts until the goldfish is a sexually mature adult fish.

One of the most exciting and rewarding parts of owning goldfish can be seeing them give birth to a new generation of baby goldfish.

Successfully breeding your goldfish shows you have taken good care of them.

And it gives you new baby fish to look after!

While it is possible for goldfish to reproduce in a tank, a lot of factors need to be right for this to happen.

It’s up to you to ensure that your goldfish have the conditions that encourage them to breed.

In this article, we look at how goldfish mate and the ideal conditions for mating. [Read more…] about How do goldfish mate?

Goldfish breeding is not an easy task. Unlike livebearers, such as guppies, goldfish can be relatively difficult to breed in captivity.

In order to breed successfully, goldfish need their usual quality care – including plenty of space, good nutrition and excellent water conditions – plus specific temperature changes to induce breeding.

Before commencing a goldfish breeding program, always think about the amount of tank or pond space available to you. Do you have room for new fry in addition to your existing fish? If not, don’t try to breed goldfish!

If you do have enough space then read on to find out how to breed goldfish properly… [Read more…] about Goldfish breeding: How to breed goldfish

Can goldfish get pregnant? How do you tell if you have a pregnant goldfish and what is a pregnant goldfish called?

To answer these questions, we first need to know whether goldfish carry their babies in a womb.

Do goldfish give birth to live young? Or do they lay eggs? Read on to find out… [Read more…] about Pregnant goldfish: Can goldfish get pregnant?

Do goldfish lay eggs? Yes, they do! And they don’t just lay one or two… they lay lots of them!

It’s one of our favorite goldfish facts that a female goldfish can lay several thousand eggs in one spawning!

However, before you get too excited and look forward to breeding goldfish, we should point out that it’s not easy. It’s actually quite difficult to raise goldfish to maturity, have the female lay eggs, and look after the eggs, all within a home aquarium.

In order to encourage goldfish to mate and have the female lay eggs, you’ll need quite a big tank, lots of plants, the right temperature, and your goldfish will usually need to be a few years old.

What do goldfish eggs look like?

You won’t be surprised to hear that goldfish eggs don’t look like the eggs in this picture!

Goldfish eggs actually look like small round “bubbles”. They’re clear in color except for a small dark spot in the middle of the egg. If your goldfish do lay eggs then you’ll probably find them attached to a leaf or piece of plant.

It’s because goldfish lay eggs – rather than live young – that there’s actually no such thing as a “pregnant goldfish”.

What should I do with eggs that I find in my tank?

Unfortunately, goldfish will eat their own eggs, so if you want the baby goldfish to have a chance of hatching, you can’t just leave the eggs in the main tank. You must remove the eggs from the tank or pond as soon as possible.

Hopefully, you will have prepared a small fry tank before the eggs are even laid. You can find out more about this in our article on goldfish breeding.

If you do have a fry tank ready then you can move the eggs – or even the whole plant or spawning mop that the eggs are attached to – and put them into the small tank. If not, you’ll have to quickly find a temporary container!

Whatever container you use, you should ensure that the fry tank is a similar temperature to the main tank – between 20°C/68°F and 23°C/74°F. Use a heater to slowly raise the temperature of the water if necessary.

Finally, you don’t necessarily have to transfer all of the eggs to the fry tank. Lighter colored eggs have a much greater chance of hatching, so you can dispose of dark eggs and only transfer the lighter ones.