Easy Guide for Goldfish breeding in Aquarium 2021

Last Updated on December 30, 2021 by cmoarz

It’s only natural to think about goldfish breeding, especially if you have a pair of really nice (and expensive) fish. Luckily it’s not very hard and all you need is a few instructions and some preparation. Let’s take a look at the breeding instructions bellow.

There is a different between Goldfish breeding in a pond and in an aquarium.

In a pond, Nature usually takes over and the gold fish don’t need any help.

The problem with an aquarium is the lack of space, lack of plants and lack of oxygenated water.

Goldfish need these 3 things if you want them to start breeding. 2 of the 3 are easy to fix, Add more aquarium plants for the goldfish to attach their eggs too, And get more oxygenators. The third step is where it gets a bit tricky.

But let’s get into that later, First, let’s figure out what you need to do to get the magic happening.

How to sex your goldfish

You can only sex your goldfish during the breeding season, which usually starts in April and ends in August. Your fish will start to be mature enough to breed at around 2 years old, however, some won’t breed until they are 3.

A female fish will:

  • Have a round, thick stomach and overall body will be thicker
  • If seen from above will look more circular than the males
  • Once she’s ready to breed a row will start forming on her rear which will bulge out noticeably.

A male fish will:

  • Have white speckles on their gills, called tubercles. These are only visible in the breeding season in young fish, and older fish may always have them.
  • White specs may form on other places of the fish as well
  • A thing, agile and long body shape
  • The male fish will often chase a female during the breeding season, following her like a lost puppy in love. But you can’t count on this because if there are no females in the aquarium with the males they will chase each other. Fish hormones ya know’.
Breeding stars on male goldfish, aka Tubercules for breeding

We should talk more about the chasing behavior when goldfish breeding as that is going to be your biggest indicator of a male fish.

While it may appear quiet aggressive, it’s normal and usual and you should not be worried about it.

All the males want to do is force the female into a tight spot up against the glass and aquarium plants. This forces the female to spawn her eggs. He won’t hurt her.

He just wants to bust a fish nut. We’ve all been there!

A friend of mine

In case it wasn’t clear, Goldfish don’t have “sex”, they release 2 types of rows. One soft (male) and one hard (female) and all fertilization takes place outside the body. The female can lay up to 1000+ eggs at a time, but only a handful will become fertilized without human assistance.

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Goldfish Breeding Cycles

Interestingly, it’s not the male who starts the breeding cycle. When the female is ready she will release a set of pheromones into the water that will force the male goldfish around her to get ready for the goldfish breeding cycle.

Keep in mind tho if it goes on for more than a week, remove the female, so she can have a break.

This also kicks off the production of the soft roe (milt, which contains the sperm).

I would say the most important step in the process is going to be patient. Unless you’re a seasoned fish breeder, You may not be completely successful the first time.

Worst yet, Sometimes it will just happen naturally and all your prep was for naught. That’s nature for you. There are some things you can do to help the process along and speed it up a bit:

Speeding up the process

  • Goldfish like heat, That’s when they like to breed. Adding an aquarium heater into your tank will definitely help this process along. Keep the tank at a nice 70f(21c) during daylight hours and 50f(10c) during night hours. Most heaters have timers.
  • Adding additional nutrients to their diet will also make a difference. You can either buy premix for breeding or just add things individually. You should be looking for proteins, blood worms, dried larvae, brine shrimp, etc. Some dried fruit and very flakes will also help keep their digestive systems running clean.
  • Feeding will often help start the breeding process, at least 3 times a day. Keep in mind that increased food will call for an increased water change schedule, which brings us to the next tip:
  • Goldfish breeding is best done in clean water, so do a partial 10-20% water change every single day during the breeding season. It’s a lot but necessary.
  • Have a ‘fry’ tank ready to go in advance. You will need to place the baby spawn in a separate tank from the adults. Goldfish will savagely eat their own young.
  • If you find your goldfish breeding isn’t going so well and the fish are being stubborn, Try splitting the males and females apart for a couple of days. Place the males in your prepared fry tank. This may increase their desire to reproduce once reintroduced. (DO NOT place adults in the fry tank if there are already fry there.)
  • Make sure there are plenty of aquarium plants for your fish to attach her eggs too. Goldfish are very unlikely to breed in a sterile empty tank.

How to set up a fry tank

It’s vital you have a fry tank set up and ready to go for after your goldfish breed if you want them to survive.

It’s really simple, here are the instructions:

1. Any size aquarium will do, I recommend 10 gallons.

2. The water should be the same temperature as the main aquarium.

3. Use a filter specially designed for fry, Which is low powered. They are usually covered in preferred foam so the baby fish don’t get sucked up.

4. The tank should have no gravel or sand in it. Keep bare glass.

5. Keep the water level shallow, no more than 15 cm(ca. 6 inch). This makes it easy for the fry to come to the surface and eat their food.

6. Catch the eggs from the main aquarium and gently place them in the fry aquarium. You can use a small net for this, Or, if you had a spawning mop set up, just gently shake them into the fry tank.

7. Keep the water at a constant 70f(21c) and the eggs will hatch in about 4 days.

8. Cloudy eggs are dead, remove them.

9. Frys are small and need a special liquid diet before they are big enough to feed on adult food flakes. This will last about 2 months. The food isn’t expensive and you can buy it at any local pet store or on Amazon.

Goldfish fry should be fed at least 5-6 times a day, but generally, just go with your gut. If they are eating a lot of food within the first 2 minutes then increase your feeding schedule. Try not to overfeed the fish do your best to keep the water as clean as possible, It might be hard with a liquid diet.


Owner of AquariumGravel.com and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!