How to Tell If a Goldfish Is Pregnant

Goldfish are a popular option for people looking for a pet that is very easy to take care of. In comparison to dogs, you will not have to go regularly for walks. Plus, they will not go and destroy the house when you spend too much time at work. While goldfish are truly low maintenance, they still are live animals that need care and have normal bodily functions. This includes reproduction.

Population control of goldfish is not a big concern. But if you are interested in having little baby fishes, then you will definitely want to know all about goldfish pregnancy.

Do Goldfishes Actually Get Pregnant?

“Pregnant“ is not actually a word that applies to goldfish. This is because, while they do reproduce, they do so in a very different manner compared to humans. They are not able to support and grow a fetus, nor do they give birth to one. Goldfish are oviparous, so they develop eggs that they release. These eggs are then fertilized and eventually hatch.

Breeding your goldfish is possible, it is also fun and not difficult at all. This process is called spawning but in order to have some little baby fishes in your tank, you will need to have both male and female goldfish living together in the same tank.

At the right time, the mama goldfish will release the eggs to be fertilized by the papa. However, it is important to note that you will need to keep the eggs somewhere else because goldfish tend to eat their young.

Determining A Goldfish’s Sex

As this whole process is dependent on actually having both female and male goldfish, you might want to figure out the sex of your pet. Even if you are not interested in breeding them, knowing how to identify their gender will help you avoid any unwanted surprises. This means, if you end up having both sexes due to some uncontrollable circumstance, then you can at least take the safer route of separating the 2 fishes.

Female goldfish can be identified through 3 characteristics. First, it should have a full and round belly even though it is not pregnant. Second, it has rounder and shorter pectoral fins (the ones behind the gills). Lastly, a female goldfish has an anal vent that protrudes more and is slightly thicker, which gets more prominent during the breeding season.

Unfortunately, these signs are quite subtle and it takes a keen or experienced eye to differentiate the male or female goldfish for sure. Knowing these characteristics can probably be helpful if you are curious as to what your pet’s gender might be, but if you really need to know, then you can always ask your vet.

Take a look at our review of Fish Bowls for more options. 

Signs of A Female Goldfish Ready To Reproduce

While determining a goldfish’s sex is complex, figuring out whether it is ready to lay eggs is much easier. Much like many other animals, they breed at a specific time, when the conditions are perfect. Moreover, you will be able to see behavior changes and even physical evidence of the eggs being spawned or released. If you do not want to be staring at your tank for a long time waiting for your female goldfish to lay its eggs, you can invest in a thermometer to check whether the conditions are ripe for some goldfish breeding.

• The Breeding Season

Goldfish reproduction is not necessarily dependent on the time of year. Instead, the goldfish require a specific temperature so that the female releases its eggs. During spring or summer, when the water reaches 68 degrees Fahrenheit, the cycle starts. However, if you have an indoor tank and you keep your home warm all year round, then it is possible to see your female fish releasing hundreds to thousands of eggs.

These eggs get released close to any vegetation on the tank, normally during the early hours of the day. The male goldfish then race to release their milt in order to fertilize these eggs. Within 3 to 4 hours, it’s all over and the eggs can be seen stuck to the vegetation. If they are unfertilized, then they are white in color. On the other hand, fertilized ones are golden brown and transparent.

• The Female’s Readiness

Goldfish have to first be older than 1 year to be ready to reproduce. After this, you will see some physical changes that signal that it will release its eggs soon. First of all, the bellies look fatter and bigger. They will also develop some white bumps on the pectoral fins (the ones on their sides) and gill covers.

If you observe your pet’s behavior thoroughly, you might also notice some signs in their actions that signify that they are ready to release their eggs. They may start to “nest”, or hiding in plants or shelters, moving slower than usual. They end up feeding differently as well. They normally eat less when they are about to release their eggs, with some fish even refusing their food.

• Male Behavior

Males of various animal breeds can also detect when females are ready to spawn. They will start to act differently, but they are certainly aware of the impending egg release.

First of all, they develop some tubercles or small bumps colored white that appear on the gills, head, and pectoral fins. Second, you will observe the males starting to chase the female goldfish around. The male goldfish will try to bump the bellies and sides of the female so that it starts to release the eggs.

• Eggs Falling Out

In some cases, you will see the eggs themselves coming out of your goldfish when she is fertile and ready to spawn. You may notice it when trying to pick up your fish or catch it to move it from its tank. As mentioned above, the males will also try to help out in releasing these eggs by bumping into the female.

A word of precaution though, you should never try to squeeze any eggs out yourself, as it can cause both stress and damage to your goldfish. If in the extreme case, the eggs are unable to get out and get impacted, then you should refer to a vet or a breeder to help your pet out. This may happen when there are no males around to fertilize the eggs and this can result in an unusually large abdomen.

Check out our guide on Aquarium Heaters for more info. 

What Happens To Eggs That Get Fertilized?

In the lucky event that the eggs were fertilized, these eggs will hatch after 2 to 7 days. However, it can be faster or slower depending on the temperature of the water.

If the water is very warm, or at minimum 84 degrees Fahrenheit, they will hatch within 46 to 54 hours. If it is only between 70 and 75 degrees, then it will take 5 to 7 days. They have yolk sacs that will provide them food for 2 to 3 days. For parent goldfish that have empty sacs, you can expect them to even target their own young.

Breeding Goldfish Successfully

If you want your fish to multiply, then you do not really need to do much other than making sure you have a pair of male and female goldfish. You will also want to monitor the temperature of the water, keeping it warm indoors to promote breeding.

On the other hand, caring for the eggs and the fry (baby goldfish) is more challenging because adults have been seen eating them. Thus, you need to take some specific steps to take care of the little ones.

• Add a spawning mat or you can create one using a new and unused mop head. There are also breeding tanks for those who are really into goldfish breeding. These tanks will immediately separate the eggs, which fall through slots in a V-trap and they can be easily transferred after being fertilized into a separate fish tank.
• If you are doing it with a mop head, you will need to watch out for signs of spawning. This normally occurs early in the morning and lasts 3 hours.
• After eggs are released, watch out if any have been fertilized. They can be easily identified through their golden brown color, while unfertilized ones remain white. Fertilization should happen within 12 hours after spawning.
• Separate the fertilized eggs into a new tank that has a filtration system like a sponge or a system placed under the gravel. This is important to ensure that a fry does not get sucked up into the filter after it hatches. Try to remove any egg pieces after they hatch.
• After a while, you will start to see little fishes swimming in the tank. They will be born with their own yolk sacs that provide them with food but when these are empty, you will need to feed them. Brine shrimp, fry food, or daphnia are the best food options for your little ones.

Although the female goldfish spawns hundreds of eggs, it is perfectly normal that only a few of them survive to become fry and reach adulthood. To increase chances of survival, you should invest in the right equipment.

You may also like our article on Protein Skimmers.

Goldfish breeding is quite an interesting, albeit complicated, process, especially if you are interested in expanding your brood. In order to successfully do so, the right knowledge is required. Because they are fish and not human, they do not become “pregnant” like you or other mammals. Instead, they lay their eggs to be fertilized. When you understand this process, you can be successful in creating your little goldfish family.