Swordtail Fish Water Temperature

Swordtail fish are popular species of fish among aquarists. They are easy to take care for, and have a calm attitude. Swordtail fish are also known as Xiphophorus Helleri.

They are freshwater fish species that belong to the brackish fish in the Poecilidae family. Swordtail fish are livebearers like guppies, mollies, platies and the mosquito fish.

Unlike many other types of fish that lay eggs and hatch them into young fish, live bearers, such as swordtail fish, get pregnant and give birth to swordtail fish babies, called fry.

Swordfish are native to Central and North America. In the wild, swordtail fish are olive green in colour with red and yellow stripes along its two sides.

They are also known as either green swordtail fish or red swordtail fish. Today, we have many types of swordtail fish with a variety of colours.

This is as a result of interbreeding done by most fish breeders. If you are considering to keep swordtail fish in your aquarium, you need to know some basic needs of the swordfish.

Swordtail Fish Best Water Temperature

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Swordtail Fish Best Water Temperature

Swordtails can be kept in water temperature ranging between 65 to 82 °F (18 – 28 °C). But which is the best water temperature to keep, breed and raise swordtails?

Below you can find all the information you want regarding swordtail fish water temperature.

Best Water Temperature for Breeding Swordtail Fish

There are different things that you can check to determine the gender of your swordtail fish. Fist, the males have an extended sword like tail that extends from their caudal fin to almost half the size of the male fish.

This is the main reason why they are referred to as swordtail fish even though the female have no such extension. The female have a rounded tail fin. Their bodies are fuller and more rounded compared to their male counterparts. They are also longer than the male when they reach maturity.

Apart from the sword like extension, the other difference between male and female swordtail fish is the gonopodium. The gonopodium is primarily for sexual characteristics unlike the sword that is only for show. Gonopodium is a modified anal fin.

It is a long tube that has a hook like end that male swordtail fish use to inseminate the female with. Male swordtail fish may from time to time be seen swinging the gonopodium for show off.

Swordtail fish male babies are not born with the sword extension nor do they have gonopodium. When they get to approximately the age of six to twelve weeks, the gonopodium appears first, then the sword starts to develop at the age of around eight months. However, there are some exceptions, these time limits may differ for different swordtail fish.

Breeding for swordtail fish can start at any time from their third month of age. If you are not ready to get many more swordtails fish, the best way to control them is to separate male and females.

When a female swordtail fish is pregnant, its belly becomes bigger, they exclude themselves from male swordtail fish and become aggressive towards the male.

They also hide in one corner of the aquarium and confine their movement within a small perimeter.

The best temperature for breeding swordtail fish is around 78 °F (25 °C). Other water parameters such as PH, and water hardness level should be kept at optimal. Check the concentration of ammonia and nitrates too, to ensure they are not too high. Poor water conditions can lead to stress and loss of pregnancy.

Female swordtail fish can produce 50 to 100 fry in one pregnancy. After giving birth, they rest for around four to six weeks then they are ready to give birth again. Second pregnancy can take place even in the absence of a male in the tank.

The female swordtail fish have the capability of storing male sperms cells in their pouch and fertilize them when they are ready on their own.

When the fry are released into the water tank, they are at a risk of being eaten by the adult swordtail fish. Therefore, when the fry are born, consider moving them into a different tank for their safety.

The fry are small, the size of the point of a pen and as clear as bubbles. Use a fish net to transfer them to a different tank.

A female swordtail fish can interbreed with male from other fish species, for instance the platy family or the guppy. This results in a variety of colourful fish with different size and shape from their parents.

In a new tank, a female swordtail fish may ignore a male swordtail fish. However, this does not mean she is uninterested or unable to mate, but she is probably trying to adjust and get comfortable in her new environment.

Remember, male swordtail fish will always run around in the tank in attempt to mate with the female swordtail fish. Therefore, ensure the male swordtail fish are more than the female in the tank.

Minimum Water Temperature for Swordtail Fish

I would not advise you to keep your swordtail fish under 65 °F (18 °C). In lower water temperature the risk of developing a disease is very high.

I’ve tested different water temperature with swordtails and I know that they can survive even in 55 °F (13 °C) temperature water. Though, they become inactive and lose appetite. Beside this, they will lose their color and will become pale.

Maximum Water Temperature for Swordtails

I’ve kept swordtails with discus fish together. Discus fish need higher temperature to feel comfortable. They enjoy 90 °F (32 °C) water temperature or even above. Swortails will also tolerate these higher temperatures, but it is not ideal for them.

Make sure you provide good water circulation and oxygenation at higher temperature, because above 86 °F (30 °C) oxygen level can get critical for most fish.

Swordtail Fish Housing

Swordtail fish are average sized. The male fish grows to around 5.5 inches, which is somewhat smaller than their female counterparts that grow to around 6.3 inches.

However, despite their small size, they are active swimmers, therefore they could a larger water tank could befit them. For one adult swordtail fish, the minimum tank size should be not less than 15 gallons.

If you want to add one more adult swordtail fish, then the minimum size should be at least 30 gallons of water. Male swordtail fish are highly territorial. To ensure the females are not harassed, consider a ratio of 1 to three or four females in one water tank.

Apart from being active swimmers, swordtail fish are also good at jumping. To avoid accidents consider having an aquarium cover for your swordtail fish tank.

Swordtail Fish Water Parameters

Most aquarists find it easy to keep swordtail fish because they are tropical fish that can survive in a wide range of water parameters. However, to keep your swordtail fish healthy and comfortable, avoid abrupt water temperature changes or very low water temperatures.

This can make the swordtail fish’s immune system to get low leading to more serious health issues. Swordtail fish are comfortable in water temperatures between 65 and 82 degrees Fahrenheit.

Swordtail fish thrive in alkaline, hard water. The ideal water PH for a swordtail fish water tank should be between 7.0 and 8.4 with hard water from 12 to 30 DH. To ensure the water parameters in you aquarium are always optimum, make sure the water is properly filtered. You should always monitor water parameters in your aquarium to prevent potential complications and health hazards.

For your swordtail fish tank, you can get a few devices to help ensure your fish is comfortable. Get a thermometer to maintain the water temperatures, and a water filter to ensure the water quality is always high. You will also need to clean the aquarium a few times in the month as well as change the water.

Feeding Sowrdtail Fish

Swordtail fish are omnivores. In their natural habitat, they eat insects, algae and other sea vegetation. Make sure you feed them enough proteins and vegetation to satisfy their diet needs.

You can feed them quality flake food or like foods such as brine shrimp, mosquito larvae, bloodworms or fruit flies.

Swordtail babies need food as soon as they are released into the water. You can feed them finely crushed flakes and newly hatched brine shrimp.

Swordtail fish are not fussy eaters. They can feed on anything offered to them. It is important that you note, swordtail fish will continue eating as much food as you feed them.

This could lead to health issues. Therefore, you should feed swordtails small pinch of food two to three times a day.

Swordtail FishTank Mates

Swordtail fish are peaceful and calm fish. They are social types that live in groups. They enjoy good company from other fish, especially their own kind.

They can live peacefully with other similar species of fish such as angelfish or mollies. Other large fish such as tetras can also live well with swordtail fish. However, to avoid harassment in the tank form the larger species, keep the swordfish in schools of five or more.

Male swordtail fish are territorial. They will become aggressive to other males of the same species that threaten to invade their space. To ensure they is peace, keep a male swordfish in a water tank with two or three female if the aquarium is not big enough.

Swordtail Fish Life Span

The average lifespan of swordtail fish is approximately 3-4 years, though this really depends on multiple factors. One of the factors that will affect swordtail lifespan is water temperature.

Warmer water will speed up the metabolism of the fish and therefore their lifespan will be shorter. On the other hand, warmer water also helps in growing swordtail fry more quickly.

As swordtails get older, they become more lethargic, decline in size and their colours appear faded.

This is evident mostly on female fish due to strain of giving birth. However, some swordtail fish die earlier than others. Death is mostly not caused by age, but what mostly kills them is physical stress that may be caused by poor water conditions or diseases.


Swordtail fish are among the most popular species of fish among aquarists. They are flexible and can survive in different water conditions.

However, to ensure your finned friends are always healthy and comfortable, it is important to ensure you keep water parameters at optimum. As I mentioned before, the best water temperatures for swordtail fish is between 65 and 82 °F.

Questions and Answers

Douglas Medlin February 6, 2020 Reply

Does water temperature determine if spawn is more one gender or the other.

    I’m not sure if temperature will affect the distribution of genders in swordtail fish. From my experience of breeding swordtails, guppies and other live-bearers, I found that in colder water, there are more male fry, but I can’t say if for sure that the temperature is causing this or it is only genetics. I shall conduct an experiment on this and eventually do more research.

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