Goldfish Eggs in Tank: What to Do? and How to Take Care?

If the thought of having new baby goldfish is appealing to you, then you will need to learn all there is to know about achieving the best results when breeding your goldfish and having goldfish eggs in the tank.

Naturally, when it comes to breeding goldfish in an aquarium, it takes more than sticking a male and female goldfish together; it takes careful planning, patience, and some serious dedication. Nevertheless, if you are determined to make breeding goldfish a new hobby, here are all of the basics of what beginners need to know to make the ideal fry.

At what age can goldfish start breeding?

The earliest that you can start breeding Flipper and “Flipperette” is at the ripe old age of 2, but many goldfish experts believe that it is better to wait until they are at least 3-­5 years of age, to ensure the best breeding results. Once your goldfish are old enough, carefully select the best-looking fish. You won’t want to limit yourself to only two goldfish, because it is recommended that if you want the best results, you should have two males for one female when breeding. For this reason, it is a good idea to select at least 6 goldfish.

How can I tell the sex of my goldfish?

One way of determining the gender of your goldfish is through vent sexing. Vent sexing is the method of distinguishing sex by observing the appearance and shape of the anal opening. Sounds fascinating does it not? Bet you were just dying to observe your fish’s butt! All kidding aside, this is a difficult process that is best left to experts.

However, if you are determined to give it a try, you will need to purchase a good magnifying glass, like those used by jewelers, as well as make sure you have good lighting. The vent is the opening located beneath the anus and above the anal fin and is where sperm or eggs are excreted during spawning. The vent of a female is substantially larger in diameter than that of a male and is usually darker in color (depending on the breed of goldfish).

4 Goldfish in aquarium

What are the signs to know if my goldfish is going to have babies?

You will know if your goldfish is going to have babies by observing the above-mentioned spawning characteristics in your fish. However, if you want your goldfish to breed and have their offspring survive, you will need to follow certain criteria to ensure that you achieve the best breeding results. You will also need to take specific precautions ­after the spawning is complete ­in order to protect the eggs and newborn fry from being eaten by their ever-hungry parents.

How do I successfully breed goldfish?

After you have made the decision to breed your goldfish, you will then need to begin planning almost one year in advance before the actual spring spawning season takes place. First, you will want to remember to pick the best-looking goldfish and don’t limit yourself to two. You don’t need to select specific female fish to attract male fish when breeding, or vice versa, you will simply want to make sure that you have two males for every one female to achieve the best results. To avoid accidents, once you have your breeding goldfish selected; separate the males from the females during the pre-spawning season, until you are ready to breed them.

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Water temperature for goldfish breeding

In order to breed goldfish, you will need to manipulate the natural cycle that would occur if they were living in a pond or in the wild. In the fall, feed your selected breeding goldfish a variety of live foods such as brine shrimp, chopped worms and duckweed, along with good dry food. This will help to produce quality eggs when it comes time for the spawning season. As fall continues to creep by, reduce the water temperature in your fish tank to 35-­40 ºF (2-­6 ºC) for two months, and begin to feed your goldfish very little ­about three times a week.

After the two months are over, gradually begin to raise the water temperature until it reaches 50-­60 ºF (10-­17 ºC). This stage is what is known as the pre-spawning period, which lasts for about four to six weeks. During this period you will want to slightly increase their food, but still continue to feed them light amounts only three times a week.

Once the spawning time arrives, you will then want to raise the temperature so it is in between 65 -70 °F (18-22 °C). As soon as the temperature is raised these extra few degrees you will notice a change in your fish.

White Goldfish

Preparing the breeding tank

Once your goldfish are ready to go, you will need to prepare for them a nice little breeding pad, where they can happily do their thing. For best results, use a tank that is at least 20 or 40 gallons (75 or 150 liters) in length. Basically, the size you will need depends on the number of fish you are breeding, as well as the number of plants and spawning mops you choose to place in the tank.

You should stock your goldfish tank with a variety of non­abrasive aquarium plants, such as artificial spawning grass, floating rooted plants, bottom plants, ponga fronds, soft willow and spawning mop. You can make the spawning mop yourself or purchase it along with the other required plants at a pet shop. If you choose to make spawning mop, make sure you use acrylic yarn, and clean the pieces first in hot water, to remove any excess dye or germs, and let them dry before placing them in the tank.

You will want to place a sufficient amount of these plants in the breeding tank, to not only entice your fish but also to serve as good hiding places for the sticky eggs that will be dropped all over the tank during spawning. This will also make it easier for you to move the eggs to safety once the breeding session is over.

How do goldfish reproduce?

If your breeding tank is ready to go, reunite your separated goldfish and watch them work their magic. Usually, breeding will begin after a storm or when there is a dramatic change in barometric pressure. This being the case it often occurs in the morning and can last anywhere from 3 to 6 hours.

You will notice that when the goldfish are ready to reproduce, the fish remain close together; they will rub against the spawning mops, as well as each other. Male goldfish will eventually begin to chase after the females and nudge the female’s anal and caudal area. At this point, the females will begin to release their eggs, and the males will follow suit and release their milt (sperm) to fertilize the eggs.

Goldfish eggs

Depending on the size and state of the female, approximately 500 – 2000 eggs will be released during the breeding period. All eggs will stick to the first thing they touch ­even the ones that are infertile. You will be able to tell the difference between infertile eggs and fertile eggs by their appearance and color.

Infertile eggs will turn white/opaque and fuzzy within the hour, whereas fertile eggs will be a yellow-amber color, and are approximately .01 of an inch (approximately 1.5 mm) in diameter. You will want to move all infertile eggs as soon as possible, because they will quickly begin to decay, and can affect the health of the fertile eggs.

Goldfish In Breeding Tank

Taking care of the small fry

Once breeding has been completed, remove the eggs and spawning mops from the tank ­to save them from being eaten by the adult fish ­and place them in another tank that has the exact same temperature of well­aerated water. For eggs to hatch within 3 to 5 days the water temperature should be in between 65-­70 °F (18­-22 °C). You will want to keep this temperature for a total of 8 or 9 days, to allow the newly hatched ¼ of an in. (just over ½ of a cm) fry time to absorb all of the nourishment from the yolk sacs attached to their bellies.

Any of the infertile eggs that do not hatch (remember they will look fuzzy and white/opaque in color, unlike the pale amber­yellow of fertile eggs), should be removed immediately from the tank to ensure harm does not come to the newborn fry. Once removed, add about 10 drops of 1% Methylene Blue per 2 gallons (10 liters), to control any growing fungus.

You will not begin to feed the fry until they have finished their yolk sacs (usually after 3 days from hatching). However, you will want to immediately feed them after this time with newly hatched brine shrimp, or with sifted daphnia. Be careful not to over­feed them, and immediately remove any uneaten food from the tank, because any food that is left to decay will kill the fry, due to the fact that they are highly prone to sickness at this fragile stage of life.

This being the case, you will also want to make sure that you are using a sponge filter that has low turbulence to keep the water environment of the tank healthy. In addition, you may wish to keep all of the fry produced, or after two weeks, you can select and remove any unwanted fish with the help of a magnifying glass.


Remember, as long as you maintain high water quality in your fry tank, feed them plenty of good food, and give them lots of room to swim, you will be amazed at how fast your fry mature and grow into fine young goldfish.

You will be able to tell if your goldfish are ready to spawn is by observing the change in your fish’s appearance. If you want your goldfish to breed and have their offspring survive, you will need to follow certain criteria to ensure that you achieve the best breeding results.

You will also need to take specific precautions, after the spawning is complete, in order to protect the eggs and newborn fry from being eaten by their ever-hungry parents.