How Fast Do GoldFish Grow? The Comprehensive Guide

Are you excited for your baby Goldfish to grow into an adult? Or are you worried that your Goldfish is not growing fast enough? Maybe there is something that you are not doing right. Well, no need to worry. I will answer the most commonly asked questions as to how big a Goldfish can get, and how can they reach their maximum size.

Goldfish grow very fast in the first two months. After 9 weeks of age, their growth becomes slow. Goldfish grow approximately 1 inch every year. If you give them the perfect environment with highly nutritious food then you can increase their growth rate.

How Fast Do GoldFish Grow?

Goldfish have been known to grow as much as 12 inches not just in the wild but in aquariums as well. The largest recorded Goldfish was in Holland, it weighed 3 pounds and was 18.7 inches in length. Another Goldfish in the UK weighed about 2 pounds and was 15 inches in length at the age of 15. You can see that Goldfish can grow up to great sizes, but how to help them grow big and grow fast is the real question. So, let me tell you how you can help your Goldfish grow.

How fast do baby GoldFish grow?

As with humans, our children need proper care and nourishment in their growing ages. The same goes for Goldfish, in their early stages. Baby Goldfish or Goldfish fry need proper nutrients for proper growth and development. So, you must ensure that when your Goldfish hatches, it is kept in the best environment possible. Let me explain the growth process and guidelines for your newly hatched Goldfish fry in the first few weeks.

GoldFish Baby Growth
  • Week 1: This is when your Goldfish has just hatched and is taking in the environment around it. Make sure that the temperature of the water in your Goldfish tank is around 75 °F at the time of hatching. You will observe that within half a week, the Goldfish fry will begin to swim around and will be about 5 mm in length. This is the ideal time to feed your baby Goldfish their maximum protein. You can do this by feeding them brine shrimp, bloodworms, and daphnia.
  • Week 2: By the second week your Goldfish fry will have grown to about 7 mm in length. Do not stop feeding them a protein-rich diet.
  • Week 3: You will observe that by now the dorsal fins of your Goldfish fry will start to develop. The fry will have grown to about 11 mm in length.
  • Week 4: The Goldfish fry will now be developing the other fins after their dorsal fins are fully developed. This is high time that you feed your Goldfish more protein as their fins will be developing.  They will have grown about 14 mm in length by now.
  • Week 5: With all the fins being fully developed, your Goldfish must be swimming more freely. But their eyes still have to develop, which will start in the fifth week. Some Goldfish, depending on their type, will darken in shade.
  • Week 6-7: By this time, their eyes will have fully developed. Your Goldfish is now a complete fish and will be as much as 20 mm in length. Do remember to keep feeding your Goldfish all the protein that they need in the form of meaty foods, like bloodworms, and brine shrimp.
  • Week 8: In the eighth week, your Goldfish fry will have grown as much as 26 mm in length. It has now fully developed and needs other dietary elements in its diet too, like veggies for fiber.

How Fast Does a Fully Matured GoldFish Grow?

Now that your Goldfish has grown up fully, you must be asking how much they grow after this. Adult Goldfish can grow one inch every 12 months. This can vary from specie to specie, but better conditions can increase their growth. Goldfish can live as long as 20 years, and if they are kept in proper conditions, you can help your Goldfish grow as big as the largest Goldfish ever known. Or maybe even bigger than that!

How to help your GoldFish grow?

You can certainly increase the chance of your Goldfish’s growth by providing them with the best care and environmental conditions. Here is what I did to help my Goldfish grow faster:

1. Regular Water Changes

You may not think of it as an important factor in the growth of your Goldfish but let me clear out this confusion for you. There are three major reasons why this is an important step in the growth of your Goldfish:

Changing Water Irregularly
  • Waste: As you must know, Goldfish like to eat a lot. Hence, they produce a lot of waste as well. This waste is mostly rich in ammonia, which is not just extremely harmful to your Goldfish but is also going to stunt the growth of your Goldfish.  
  • Low Oxygen Levels: If you do not clean your Goldfish tank regularly, and there are algae building up, the oxygen levels in the tank will drop. Your Goldfish will not have enough oxygen to breathe in, thus stunting its growth.
  • Growth Inhibiting Hormones: You must have heard somewhere that Goldfish grow as much as their tank allows them to. This is true, but it can be changed. Goldfish produce certain hormones that will stop them from growing any more than they already have. When the water in their tank is not regularly changed, the concentration of these hormones in their tank will keep on increasing. Thus, preventing them completely from growing any further.

You must change the water in your Goldfish tank once every week, by changing 25% of the water. After every month, you can change 50% of the water in your Goldfish tank. This will most certainly help them grow and stay healthy as well.

2. Large Space

If you are trying to grow your Goldfish in a regular-sized fish tank or just a bowl, you are doing it all wrong. Goldfish need a lot of space to grow. If you only have a single Goldfish, you need a tank as large as 30 gallons. If you wish to keep adding more Goldfish, you must add another 10 gallons of space. So, if you have 4 Goldfish, you must have a tank that is at least 60 gallons in volume. If you are keeping your Goldfish in a community tank, with other fish as well, you must further increase the size of the tank, as Goldfish enjoy personal space. Moreover, the larger the space is, the lesser the waste concentration will be of the water in the tank. Thus, increasing the chances of growth of your Goldfish.  In a water body as large as a pond, Goldfish can grow up to 13 inches easily. This speaks volumes about the volume of water required for your Goldfish.

Goldfish Large Tank

3. Keep Tank Less Crowded

If you are intending to grow your Goldfish to bigger sizes, you must ensure that their water tank is not too crowded. As I just discussed the tank size for your Goldfish, you must make sure that your Goldfish have proper room to grow. If there are too many fish around them, there will be more waste too. Unless you do water changes more quickly than before, your Goldfish will be subject to all this waste and will not grow to its maximum.

Goldfish less Crowd

4. Optimum Temperature

The ideal range of temperature for your Goldfish is 68-74 °F. it is better to keep them in a slightly warmer water temperature, as this will increase their growth. Keeping the temperature of your Goldfish’s tank lower than optimum will make them go into hibernation and will slow down their metabolism. This will stunt their growth. So, it is best to keep them in water at a temperature of 74 °F, which is not just ideal for the hatching Goldfish, but the growing Goldfish as well.

gold fish Water Temperature

5. Good Food and Nutrition

Proper nourishment and diet are very essential for your Goldfish to grow.

  • Quantity: Goldfish like to eat lots of food, which is because they do not have stomachs. Their food goes directly to their intestines making more room for food at all times. A Goldfish can eat as much food as the size of its eye. This is a good rule to follow when feeding your Goldfish, as you should not overfeed or underfeed them.
  • Types of Food: To make growth maximum for your Goldfish, you must add high protein to their diets. You can do this by feeding them live food, such as shrimp, and bloodworms. They also need vegetables in their diet, and you can add lettuce, peas, and carrots for better nourishment of your Goldfish.
  • When and How to Feed: It is best to follow a similar routine every day for feeding your Goldfish, as it will train their digestive systems to make them hungry when the food will be arriving in their tanks. You must feed your Goldfish 2 to 3 times a day, but the quantity should be monitored. If your Goldfish does not eat the food that you add to its tank within 2 minutes, remove the food. If you do not remove the food, it will start to decay and raise the pollutant levels in your Goldfish tank, which is not good for the growth of your Goldfish.

6. Good Genes

There is a high chance that you will grow taller if both or at least one of your parents is tall. The same goes for Goldfish. Some types of Goldfish have been growing in the wild and have a good gene pool when it comes to size. It is okay if your Goldfish is not growing even after you have tried everything. This may be because it has reached the maximum size that its genes have allowed it. For example, some fancy Goldfish can grow as much as 8 inches maximum, while single-tailed Goldfish can grow up to 12 inches even.

Does GoldFish Grow Larger in Outdoor Ponds?

Goldfish exist in the wild as well. If you have created a perfect outdoor environment like a pond for your Goldfish, to match its natural habitat, you may increase the chances of its growth.

Goldfish Outdoor Ponds
  • Cleaner Water: In a large space, such as a pond, the water is always cleaner than your indoor water tank. This is because the pond is open to outdoor air and oxygen, and has frequent rainwater being added to it. This keeps the water clean for your Goldfish to grow well in.
  • More Space: Goldfish grow more in larger spaces and a pond is a large enough space for them to fully grow. They will love to explore the large area and will enjoy the larger space as compared to the indoor aquarium.
  • Food: In the wild, Goldfish search for food themselves. This helps them find all sorts of food rich in protein, nutrients, and fiber. They can even feed on smaller fish, and plants that will provide them with the nutrients they need for proper growth.

Can Your GoldFish Still Grow After Being Stunted?

If reading this article has given you ideas to increase the size of your Goldfish, you might be just in time for it. This is only true for your Goldfish if it has not matured fully yet and has been stunted in its initial growth stages. But if your Goldfish has matured fully, in an environment where its growth was stunted, you may not have the chance to help it grow any further. This is why you must care for your Goldfish the most in its very initial stages of life.

The Bottom Line on How Fast Do GoldFish Grow?

It is not hard to help your Goldfish grow if you follow all the guidelines that I have highlighted for you in this article. Do make sure that your Goldfish is staying healthy while it grows, so that it may live longer. as per my personal suggestion, you may want to transfer your Goldfish into a separate tank when it has increased in size. With the right gene pool, and water and environmental conditions, your Goldfish may even break the world record for the largest Goldfish ever!

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