Growth Stages Of Molly Fish: Find Out Here!

Molly fish is a beautiful fish that is available in the market today. It is a peaceful fish that you can keep with other tropical fish with increasing popularity. But, you will never understand how big they are and when they will get big enough for you to breed them. I have been there, and the growth stages of molly fish are something that will leave you with more questions than answers. So, let me answer all the questions about your growing mollies.

Molly fish go through five different growth stages during their lifespan, starting from the fry stage and ending with old age. They start their journey as fry passes through the fingerling stage, juvenile stage, adult phase, and reaches old age and die after 3 to 5 years.

What you feed your Molly in each stage will depend on what stage it’s in and how big they get in that stage. Similarly, you need to maintain the water parameters of the molly tank if you want to see all the stages they pass to become a healthy adult.

I know the questions and queries will make you more frustrated when the answers are as short as I have given in the above paragraphs. So, let me explain it in detail below. In this post, we’ll be discussing the growth stages of Molly Fish.

Shall we begin?

What Is Molly Fish?

Mollies are tropical fish that can come in many colors, shapes, and sizes. Aquarists and breeders experimented with this fish and bred them into different types and species with beautiful colors.

Usually, Molly fish originated from the Amazon River in South America. However, they are compatible with aquarium fish species because they can live with other tropical freshwater fishes without any problem.

Molly fish usually are a group of fish that belongs to the family Poeciliidae. They are different from most other types of tropical fish because they can produce live offspring instead of laying eggs as others do. These fish have a vibrant color and are active. The way they move around the tank is a pleasure to watch.

What Are The Growth Stages Of Molly Fish?

I know the excitement and curiosity you have when you are a beginner and bring home your first aquarium. All the questions you have and the moments you get to live for the first time.

My favorite part of raising a fish is watching it grow. Unfortunately, beginners often bring home a well-developed fish and miss the first few stages. 

But if you start from the very breeding process, you will get to watch them grow from the fryling to old age within the timespan of 4 to 4 years.

The growth stages of Molly Fish are not as difficult to recognize as some other fish. Like most, the female will grow more extensively than the male, and they both have a similar appearance throughout life.

Now, let me walk through it. The different stages of growth in Molly fish are:

Stage 1: Fish Fry Stage

Well, molly fish are livebearers, so it won’t come off as a surprise that this is the first step in their growth.

Molly fish gives birth to nearly 40-60 fry in each litter. These fry are only half an inch in size so they won’t take up much space in the tank.

Still, it is better to separate fry and female molly as soon as she is pregnant or done giving birth. Mollies are famous for devouring their babies in the tank, so keeping the molly fry in a separate tank is better if you want to see all the growth stages.

Now, the fryling stage is the very first step in the life of molly fish, so it is bound to last a little longer for development and familiarity. 

This stage lasts for one to two months, depending on the diet, water parameters, and water temperature in the molly fish tank.

Molly babies look like transparent tadpoles with distinct eyes on the top. These babies need time and diet to show their real color, so don’t get desperate or heartbroken because your molly fry doesn’t seem as beautiful as molly’s parent.

Stage 2: Juvenile Stage

 Once the fry stage is done, you will see a teeny tiny development in your fish that will last for another few weeks. The period between 4th to 6 weeks is a juvenile growth stage of molly fish.

The stage your molly fry grows into is the Juvenile stage, where this molly will get nearly an inch long in size.

In this stage, you can determine the sex of the molly fish, thanks to the gonopodium in males and a gravid spot in females.

Also, the molly fish’s distinct color becomes more vibrant after this growth stage.

Stage 3: Fingerling/Teen Stage

I know it seems like a new term for most parts, but trust me, it will make it easier for you to understand what really happens.

You have seen a teenager or probably been a teenager a while ago; you know the drill about attaining sexual maturity.

Molly fish is in their teenage stage when they are between the age of 6th weeks to 6 months; it usually varies depending on how much food they get.

You can start preparing molly fish to breed at the home tank during this phase. The egg development inside a female is already happening but they won’t fertilize until and unless a male releases sperm.

In this growth phase, your molly fry will attain its maximum size between 4 to 6 inches. Yes, it is absurd to think that molly will grow more than 4 inches, but there are instances where a good diet and care have given an extra growth to molly’s size.

The growth stage is when it starts becoming a bit bigger and is less aggressive. After eight weeks, these fryling will get stronger to save themselves from the predators present in the main tank.

Stage 4: Adult Stage

The fish has reached sexual maturity during this growth stage and is about 6 months to 3 years old. As a result, it has a more streamlined appearance, and its colors have become much brighter.

Their coloration becomes more vibrant, and they start looking for partners to swim with and breed. This is the phase they will last until they become old and die. 

Most mollies you bring home are often the adult ones that are well-developed and have a distinct color and body structure as molly fish.

It’s a good idea to keep them in groups since they are generally peaceful among their species. Mollies are omnivorous.

So, you should give them both plant matter and protein-rich foods for this time to meet their nutritional demand.

The adult fish has a rounder, deeper body shape, and the male molly will start to chase females during spawning season. Mature adults can reach up to six inches or 15 cm in length if you give them proper care.

Stage 5: Old Age

Now, it is not really a phase most people want to have a conversation about. But here we are; this stage starts when your molly fish reaches 4 or nearly 5 years old.

From here onward, the growth rate slows down significantly. Old age is the stage when you need to do more maintenance on the tank of Mollies and increase the amount of food you give them.

Unfortunately, death is inevitable for all fish. If your Molly lives longer than three years, it is old age in most cases. When they reach that point, they will slowly start showing signs of dying. 

After old age, the body functions of the fish slowly start degrading. They lose their scales, are more prone to infections and disease, and need more oxygen to survive. 

When you fail to take proper care of them during old age, molly fish will die easily. So, stay attentive. They may live for some extra years.

How Can You Help In Proper Growth Of Molly Fish?

Although Molly fish are easy to care for with limited tank requirements. But still, you need to be attentive when you decide to keep them in your tank. Maintaining a peaceful and clean aquarium for the Molly fish is important. It will help in the proper growth of Molly Fish. You need to follow these steps below:

Change Water Regularly

Maintain good water quality. It is essential to change the water regularly if you have decided to keep Molly Fish in your aquarium. The best way would be to change 20-25% of the total tank volume every week or two weeks, depending on fish load and bioload. You can also use a gravel cleaner for this purpose that will help you remove the debris.

Maintain Proper pH Level

pH is one of the most important factors that play a massive role in maintaining good water quality for Molly Fish. The best way would be to maintain a proper pH level which ranges from around seven and eight(neutral).

Feeding Your Molly Fish Well

One of the most crucial things that you must be attentive to for the proper growth of your Molly fish is their diet and feeding schedule. Molly fish are omnivorous, requiring different kinds of food during their growth stage.

It can be anything from flakes, pellets, bloodworms, etc., to different types of veggies. The best and quick choice for owners would be high-quality flake food rich in proteins and fats, which will help the fish grow faster with proper nutrients.

Maintain Proper Lighting

Your tank should have proper lighting to maintain the growth of Molly Fish properly. It is essential to keep them under good light for around eight hours every day. It will help in their healthy growth and development as well.

Add Aquarium Salt To Your Aquarium Water

Yes, I know how it sounds. Adding salt to a freshwater tank, isn’t it a crime in disguise? Well, it isn’t when it comes to molly’s fish tank.

Molly fish can handle a little salt; thanks to their origin. These mollies originate from the place where oceans and rivers meet i.e., brackish waters. So they can tolerate salinity in the tank and even give you the pleasure of setting up a saltwater tank for molly fish.

The point is when you add salt to the tank, molly fish will feel at home which will fuel the growth rate. Salt will help them maintain good health, strong bones, and healthy gills.

Thus, it is beneficial for your fish because this will enhance immunity and reduces the susceptibility to diseases in Mollies.

Adding some salt is an essential part of the Molly Fish growth. Most aquarists recommend adding some salt when your fish are growing in their early stages, like when they are around two weeks old.

Proper Maintaining Temperature

It is important to maintain the correct water temperature for the proper growth of Molly Fish. Usually, the most appropriate temperature for Molly fish that can assist in their development is 78 degrees Fahrenheit. 

However, some people prefer room temperature, but it is not a good idea. Mollies will grow slower if you keep them below 72 degrees Fahrenheit, which you don’t want. You can use an aquarium heater or a chiller to keep your tank temperature right.

Place Live Plants And Decorations

Adding some live plants to your tank is essential as it will help the Molly Fish in many ways. First, they provide them shelter and a good environment that can be beneficial for their growth.

However, if you cannot find an appropriate live plant for your aquarium, you can even use artificial plants and decorations.

But still, live plants are always the best option for molly fish and they provide mollies with good shelter and food. Remember, these mollies do not like a densely planted tank as the overcrowded tank can make them nervous and anxious.

You may have to deal with some mollies jumping out of the tank when there is not enough space for them to swim.

You may want to know more about: Why Do Molly Fish Jump Out Of The Tank?

Keeping Them With Similar Species

Mollies are social and active fish that can live peacefully with other non-aggressive fishes. But keeping them with similar fish will help them to grow faster.

Similar fish species sustain themselves in a similar environment and need the same type of food. So it will be easier to take care of them.

If you keep more than one species of fish together, it is advisable to change the water often. In an overpopulated tank, there will be a lot of waste, which can cause diseases and affect other fish. Choose tank mates for mollies wisely as it can really determine how big moly fish can get.

Carbonate Hardness

You need to maintain a proper carbonated hardness level for your tank because it is important for the healthy growth of Molly Fish as well.

It can be from 0ppm to 200 ppm, which will help you know how much calcium and magnesium are present in your aquarium water that helps Molly fish in their healthy growth.

If you follow these st, it will be much easier for you to maintain a proper aquarium where Molly Fish can grow happily and well, which is the ultimate goal of every fish keeper.

How Long Will Molly Fish Live?

Mollies live for three or five years, some even longer, depending on your species. But it is challenging to say precisely how long they will live as this depends a lot on how we look after them. However, some signs indicate when your fish may be near the end of their lives:

  • Loss of appetite
  • Lethargy or sluggishness
  • Areas with no scales. Such places are often at the tail and dorsal fin- fin rot.’ Fin rot can also be fatal if it gets terrible as bacteria enter these wounds. Fin rot can also lead to a loss in coloration for your Mollies.
  • Mollies start showing strange behavior, such as hiding in a corner for days at a time or constantly swimming into the sides of their tank.

Frequently Asked Questions

How Big Can Molly Fish Grow?

The maximum size of a Molly fish is about four inches in length. However, they are most commonly two inches long when born and will grow up to around an average of three or four inches.

When Do Molly Fish Attain Sexual Maturity?

Mollies usually attend their maximum size when they are six months old. But, some can even be sexually mature as early as six months old. However, the maturity of Molly fish varies when you care for them and feed them a nutritious diet.


Summing up, we can see that Molly Fish is a very enjoyable and rewarding experience, but it also has many aspects to consider. If you want to get the best out of your fish, then remember: constantly think about what they need before contacting them! If you love them enough, there’s nothing they won’t be able to do for you.

Thank you, and I hope you found this blog post helpful. If you have any queries, please drop them in the comment section below.

Good Luck!!

Happy Fishkeeping!!