Swordtail Fish Growth Stages


Swordtail Fish Growth Stages

Swordtails are very beautiful fish and that might be the main reason why many people are buying them as pet fish.

Whether you are an experienced aquarist or a beginner, they will suit you perfectly, mainly because you will not do much to ensure proper growth and to keep them healthy.

They can live in different temperature levels, water hardness and PH levels. Their scientific name is Xiphophorus helleri. Xiphophorus comes from a Greek word meaning, “bearing a sword” or “holding a sword”.

After realizing that, I thought that the livebearer is very aggressive. But that is not the case. Swordtails are peaceful. People did not name them swordtails because they are excellent fighters.

The name relates to one of their physical qualities. The male swordtail fish have an elongated tail fin (anal fin), known as the gonopodium or sword.

In this article I will explain the growth stages of swordtail fish. These stages include:

  1. Fry stage
  2. Juvenile stage
  3. Adult stage
  4. Old stage

Now, let’s take a look to each growth stage in details:

Swordtail Fish Fry

Swordtail Fish Fry

Swordtail Fish Fry (sourceCC BY-SA 4.0)

When a swordtail gives birth, you will find many swordtail fry (between 5-80) swimming around the aquarium tank. However, the mothers do not care for the fry – it is their duty to find the best hiding spots.

Naturally, fry have to protect themselves, because the adult swordtails will eat them. When swordtail fry are born, they are very small. Their size is around 3-6 mm and they will hide most of the time.

To save them from the adults, you will have to place them in a breeding tank or a breeding box. If you don’t have this option, you can a lot of live plants or accessories in the community tank to provide them with sufficient hiding places.

At the fry stage, swordtails will eat the same type of food the adults eat. However, if you want to use flake foods as part of their food, you will have to crush it into powder to ensure that your baby fish can eat it.

Newborn brine shrimp is one of the best live food for the fry, which promotes a fast growth rate. You can also provide them with hard-boiled egg yolk because it offers a good amount of protein and fat for their growth.

By leaving the aquarium lighting on for 12-16 hours in a day, you will significantly contribute to the growth of the fish. Regular water changes are important, particularly if you prefer to feed the fry many times in a day.

Some people prefer to change the water on a daily base.

If you do a good feeding job and water is clean, in one month, the swordtail fry will become juveniles.

Juvenile Swordtail Fish

Juvenile Swordtail Fish

Juvenile Swordtail Fish

As I have stated above, a one-month-old swordtail will be in the juvenile stage. The fish will have a length of 1.5-2 cm (0.6-0.8 inches), the colors will have started showing and the sexes will be identifiable. Generally, the male swordtails are larger than the female swordtails.

Typically, the male swordtails have a sword-shaped tail, which is the male organ or gonopodium. The females have a round shaped anal fin. The gravid spots of the females become visible in this stage.

The juvenile stage is the most important for swordtails, which means that you should feed them with high-quality feed and ensure that the water condition is right throughout the day.

Some of the recommendable foods for swordtail juvenile fish are beef hart, bloodworms, brine shrimp, flakes, plankton pellets and spirulina. At 2 months, the swordtails will begin to mature sexually and they will become young adult swordtails.

Adult Swordtail Fish

Adult Swordtail Fish

Adult Swordtail Fish

At around two months, you will have swordtails in the third growth stage, the adult swordtails, having about 3-5 cm (1.2 – 2 inches) size.

They still have a long way to go until reach full size, but at this stage, the fish will be sexually active and mature, even though they are not at full size just yet.

Therefore, if you want to control the breeding, you will have to separate the males from females before they are two months old. By doing that, you will help them grow faster too.

When the swordtails reach this stage, remember to feed them with more protein-rich food and greens. Do not provide fatty foods because it will affect their health negatively.

Mainly, brine shrimp should form part of their diet each day. The other good options are spirulina and plankton pellets. They will intensify their color.

Old Swordtail Fish

Old Swordtail Fish

Old Swordtail Fish

This is the final stage of swordtails. The fish will have grown fully when six months old. At this stage, they will be 12-14 cm (5 – 5.5 inches) long including their swords.

Male have swordtails and develop longer tails and fins than the females. There are some hybrid swordtails species, in which the females also develop swordtails and their tails can reach similar sizes as in males.

At around the 2 year mark the growth rate of swordtails will slow down significantly regardless of their sex.

You will have to provide them with good quality food of several varieties to keep them vibrant and healthy as they age. Protein and low-fat food should not miss from their daily diet, but you should keep these in control.

The swordtail fish have a lifespan of 3-5 years and feeding them correctly and regularly is the only thing you should do to ensure that they attain their maximum age or beyond that.

Remember that the fish will become infertile after they reach a certain age.

Suitable Foods for Swordtails at all Growth Stages

Here are the types of foods you should provide to your swordtails and their key benefits.


Meat should be the main source of protein for your mature swordtails. At the fry stage, you should include it in the diet on a daily basis. At the adult stage, include it two or three times a week.

The best sources of protein are daphnia, brine shrimp, fruit flies and mosquito pupae. Feed them live or frozen to the fish. Frozen food is easier to find in the stores than the live one.


Vegetables are another essential part of the daily diet for swordtails. Choose spirulina and algae as the staple food of your swordtails.

Adding shredded or chopped mustard greens, spinach, peas and any other common vegetable is important.


Fruits will provide your swordtails with the nutrients, minerals and vitamins they require each day. But because they do not play a vital role in the diet of your fish, you should include them in the diet once or twice in a week.

Preferably, go for grapes and bananas. The fruits have high sugar levels, which mean that you should provide them as treats and in small pieces.

You do not have to worry about the growth stages and the food for your swordtails after introducing them in your aquarium tank.

Unless the fish is suffering from a disease that you cannot control, you should expect them to attain the age of five years.

How to Dramatically Increase the Growth Rate of Swordtail Fry?

In fact, you will have to transfer the swordtail fry to the community tank when possible so that you can provide them with the amount of space they need for swimming. But to do that, you will have to ensure that they have grown enough to escape from the aggressive mature swordtails.

Failure to provide the right food and to maintain proper water conditions may delay their growth and as a result, you might need to keep them in the breeding tank for a longer time than necessary.

As the parents, baby swordtails are omnivorous. They will start eating whatever you provide immediately after birth. Moreover, they do not need the help of adult swordtails in this regard.

Provide them with live food to facilitate faster growth and to maintain proper health. Egg yolk and brine shrimp are a perfect option. Feed them more often because they need to eat a lot of food at a go.

When it comes to the tank conditions, you will have to maintain the right temperatures, PH and water hardness.

The ideal temperature should be between 64 degrees and 82 degrees F and the PH level should range between 7.0 and 8.3. The best water hardness level should be roughly 12-30 KH.

Fry will take around six months to reach its full size, which are 1.5 inches for the females and 2 inches for the males.

Improper aquarium tank conditions will not allow the attainment of that size. For your swordtails to grow faster, maintain the right water conditions.

What is the Minimum Tank Size for Swordtail Fish Optimal Growth Rate?

Swordtails are a perfect community tank species. We both know that. But did you know that swordtails love living in fast-moving water? In their natural habitats, swordtails can grow to over 6 inches particularly because they get enough space to facilitate the growth.

Even though the swordtails we get from stores do not grow bigger than 3 inches, the size of your aquarium tank will significantly determine the growth and size.

Most of the swordtail fish owners I have talked to say that they notice slow growth when their swordtail fry are in a breeding trap or in a small breeding tank.

To facilitate faster growth and to ensure that your swordtails are healthy, you will have to buy a 20-gallon community aquarium tank – the minimum recommended size – and at least 10-gallon tank for the swordtail fry.

What is the Average Lifespan of Healthy Swordtail Fish?

In an aquarium tank that offers proper water conditions, the lifespan of a swordtail ranges between 3 and 5 years.

The lifespan of swordtails that live in the wild is longer. In the fast-moving water, aggressive species are unlikely to kill the peaceful swordtails, which is the case to expect in aquariums.

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