Swordtail Fish Hiding: Reasons and Solutions

Have you ever noticed your beloved swordtail fish hiding in the tank? Dive into the mysterious world of these little swimmers as we explore the reasons behind their antics and uncover practical solutions to make them feel right at home. Say goodbye to hiding and hello to happily swimming swordtails!

black lyretail swordtail fish

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New Environment

Swordtail fish, like any other creature, can find new surroundings a bit overwhelming. When you first introduce them to a new aquarium or tank, they might feel stressed and choose to hide in available hiding spots such as plants, rocks, or decorations. These hiding spots provide them with a sense of security as they adapt to their new environment.

Here are a few factors you should consider when setting up your tank to ease your swordtails’ transition into their new environment:

  • Aquarium Size: Swordtail fish are active swimmers and enjoy having ample space to explore. A tank size of at least 15-20 gallons is recommended for a small group of swordtails. This allows for sufficient swimming space and reduces the likelihood of aggression among tank mates.
  • Water Parameters: Swordtail fish thrive in clean water with a well-maintained pH level. Maintain a consistent water temperature (72-77°F), pH level (7.0-8.4), and hardness (10-15 dGH) to create a stable environment.
  • Furnishings: Provide plants, rocks, and hiding spots for them to take refuge in while adjusting to the new environment. Live plants such as java moss, java fern, or Vallisneria are good choices, but artificial plants can also serve their purpose. A mix of flat rocks and decorations can create additional hiding spots and territories.
  • Tank Mates: Swordtails are social fish and enjoy the company of other swordtails or compatible species like platies, mollies, or guppies. Be cautious when adding more aggressive or larger fish, as they may intimidate or harm your swordtails.
  • Acclimation Process: When introducing new swordtails to the tank, acclimate them gradually. Float the bag containing the fish in the tank for about 15-20 minutes to allow for temperature adjustment. Then, slowly mix tank water into the bag for another 15-20 minutes before releasing the fish into the tank. This minimizes stress and helps your fish adapt more easily.

Keep in mind that it’s normal for your swordtail fish to hide during their first few days in a new tank. Be patient during this period of adjustment, and soon enough, they will feel comfortable in their new environment and start showing themselves more frequently.

swordtail fish livebearers

Disease or Parasites

Disease or parasites can cause your swordtail fish to exhibit unusual behavior, including hiding. Like other fish, swordtails are susceptible to various diseases and infections that can affect their health and well-being. It’s crucial to observe your fish closely and take prompt action if you notice signs of illness.

Here are a few common diseases and parasites that may cause your swordtail fish to hide:

  • Ichthyophthirius multifiliis (Ich): Also known as white spot disease, Ich is a highly contagious parasite that appears as small white spots all over the fish’s body. Infected fish may rub against surfaces, become lethargic, and hide.
  • Fin Rot: Caused by a bacterial or fungal infection, fin rot can be identified by the fraying and disintegration of your fish’s fins. Affected fish may become less active and hide in isolation.
  • Gill Flukes: A parasitic infection caused by microscopic worms that attach themselves to the fish’s gills, causing difficulty in breathing and irritation. Infected fish may gasp at the water’s surface or retreat to hiding spots.
  • Internal Parasites: These parasites may cause weight loss, lethargy, and abnormal swimming patterns. Fish may seek shelter and hide if they are feeling uncomfortable.

To tackle disease or parasites, consider the following steps:

  • Quarantine: If possible, move the affected fish to a separate, quarantine tank for treatment. This helps avoid the spread of diseases or parasites to healthy tank mates.
  • Water Quality: Maintain optimal water quality by performing regular water changes and running an efficient filtration system. Poor water quality can lead to increased stress, making your fish more susceptible to diseases and infections.
  • Medications: Use appropriate medications, such as anti-parasitic, antibacterial, or antifungal treatments, according to the specific disease or parasite affecting your fish. Consult with an aquarium specialist or veterinarian for guidance on proper treatment.
  • Preventative Measures: Regularly inspect your fish for signs of illness and keep a close eye on new arrivals during the initial period. Quarantine new arrivals for at least 14 days before introducing them to the main tank to minimize the risk of introducing diseases or parasites.

By addressing the problem and providing timely treatment, your swordtail fish are more likely to recover and come out of hiding.

black swordtail fish

Bad Water Quality

Maintaining good water quality is paramount for the health and well-being of your swordtail fish. Poor water quality can lead to stress, making them more susceptible to diseases or parasites. In extreme cases, it can even be fatal. If your swordtail fish are spending more time hiding than usual, it’s worth checking the water parameters.

Here are some water quality issues to look out for:

  • Ammonia and Nitrite: Produced by the decomposition of fish waste, uneaten food, and decaying plant matter, high levels of ammonia and nitrite are toxic to fish. Aim to keep both ammonia and nitrite levels as close to zero as possible.
  • Nitrate: While not as toxic as ammonia and nitrite, high nitrate levels can also cause stress and health issues in fish. Aim to maintain nitrate levels below 20 ppm.
  • Fluctuating pH Levels: Swordtail fish prefer a stable pH between 7.0 and 8.4. Rapid fluctuations in pH can cause stress and negatively impact their health.

To maintain optimal water quality in your swordtail fish tank, take these steps:

  • Regular Water Changes: Perform weekly water changes, replacing approximately 25% of the tank water. This helps dilute toxins and removes waste and debris.
  • Efficient Filter System: Use a high-quality filter system appropriate for your tank size to remove waste and promote beneficial bacterial growth.
  • Avoid Overfeeding: Overfeeding can lead to uneaten food, which decomposes and negatively impacts water quality. Feed your swordtail fish small portions of food that they can consume within a few minutes, up to two or three times per day.
  • Monitor Water Parameters: Regularly test your water for ammonia, nitrite, nitrate, pH, and temperature. Use aquarium test kits to monitor these parameters and make necessary adjustments to ensure consistency.

With good water quality, your swordtail fish are less likely to feel stressed and seek shelter in hiding spots. Make it a part of your routine to keep an eye on the water parameters and give your swordtails the perfect environment to thrive in.

red female swordtail fish

Female Swordtail is Giving Birth

Swordtail fish are livebearers, which means that they give birth to live and fully-formed fry, as opposed to laying eggs. If you have both male and female swordtails in your tank, it’s quite likely that they will reproduce. During the birthing process, the female swordtail may seek shelter and hide, attempting to find a safe and comfortable spot to deliver her fry.

Here are some key aspects to consider when a female swordtail is giving birth:

  • Gestation Period: The gestation period for swordtail fish is around 28-30 days. Keep an eye on your pregnant female, and as the due date approaches, increase your vigilance.
  • Safe Hiding Spots: Provide plenty of hiding spots in the tank, such as dense plant cover, decorations, or special breeding boxes, for the female to feel comfortable while giving birth. This also offers the fry a chance to escape predation from other fish in the tank.
  • Separate Birthing Tank: If you have a spare tank, you can set up a separate birthing tank for the pregnant female. Ensure the water parameters are similar to the main tank to minimize stress during relocation. After she has given birth, return the female to the main tank to avoid the possibility of her eating the fry.
  • Feeding the Fry: Once the fry is born, they will require specialized food. Look for high-quality, finely ground fry food, or feel free to use crushed flake food as an alternative. Feeding your fry several times a day in small amounts promotes healthy growth.
  • Grow-out Tank: As the fry grow and mature, consider setting up a separate grow-out tank to provide them with more space, reducing stress and competition for resources.

Understanding and providing the necessary conditions for your female swordtail during birth can ensure a safe and stress-free experience for both her and her newly born fry. Once the birthing process has concluded, the female is likely to come out of hiding and resume her normal routine.

swordtail fish tank mates

Stress Due to Bad Tank Mates

One of the potential reasons your swordtail fish may be hiding is stress caused by aggressive or incompatible tank mates. Although swordtail fish are generally peaceful, if they feel threatened or intimidated by other fish in the tank, they might opt to spend more time hiding in an attempt to escape confrontation or attacks.

Here are some factors to consider when selecting tank mates for your swordtail fish:

  • Compatibility: Choose tank mates that share similar water preferences and peaceful temperaments. Good tank mates for swordtail fish include other livebearers (platies, mollies, and guppies), tetras, and small catfish species.
  • Aggressive Tank Mates: Avoid adding aggressive or territorial fish such as cichlids or larger, predatory species, as they may harass or even harm your swordtail fish.
  • Overcrowding: Overcrowding can lead to increased stress, competition for resources, and aggression among tank mates. Ensure you provide ample space for all the fish in your tank, following the general guideline of one gallon of water per one inch of fish.

To help alleviate tank mate-induced stress among your swordtail fish, consider the following measures:

  • Arrange the Tank: Arrange the tank with multiple hiding spots, territories, and visual barriers created by plants, decorations, or rocks. This allows the fish to establish their territories and retreat when necessary.
  • Monitor Interactions: Keep an eye on the interactions among tank mates in your aquarium. Should you observe aggressive behavior, intervene early to prevent further stress or injury to your swordtails.
  • Remove Problematic Tank Mates: If a certain tank mate continues to cause stress or injure your swordtail fish, consider removing the aggressive fish and finding it a more suitable home.

Prioritizing a harmonious tank environment and carefully selecting compatible tank mates will help reduce stress among your swordtail fish. Ensuring that your fish feel safe and secure in their tank will allow them to swim freely and reduce the need for hiding.

male swordtail fish

Improper Male to Female Ratio

In a community tank with both male and female swordtail fish, an improper male to female ratio can lead to stress and increased hiding behavior, particularly among female swordtails.

Male swordtails are known to be persistent in their pursuit of females for mating, and if there aren’t enough females to spread the attention, the constant harassment can lead to exhaustion and stress in the targeted females.

Here are some tips to maintain a proper swordtail fish gender balance in your tank:

  • Ideal Ratio: Aim for a ratio of two or three females for every male in your swordtail fish tank. This helps spread out the males’ attention, giving the females more opportunity to rest and reducing their stress levels.
  • Add More Females: If you notice that the ratio is off and females are hiding more often, consider adding more female swordtails to the tank. The additional females will help alleviate the pressure on the existing ones.
  • Separate Males and Females: If the issue persists and there’s no space for additional fish, consider setting up a separate tank for males or females. This ensures that the females are not constantly harassed and have the chance to recover from the stress.
  • Monitor Behavior: Keep a close eye on the interactions between males and females in the tank. If a particular male is exhibiting aggressive or overly persistent behavior, intervene early to mitigate the stress on your female fish.

By maintaining a balanced male to female ratio among your swordtail fish, you can create a more harmonious community in your aquarium. This reduces the chances of your swordtails hiding due to stress or harassment and allows them to display their full range of social behaviors in a healthy and comfortable environment.

green swordtail

How to Prevent Hiding Behavior in Swordtail Fish?

While it’s natural for swordtail fish to seek occasional refuge in hiding spots, excessive hiding can be a cause for concern. To ensure your swordtails feel comfortable and secure in their environment, take the following preventative measures to reduce hiding behaviors:

  • Set up Proper Tank Conditions: Ensure your tank is set up with the right size, water parameters, and furnishings to create a comfortable environment for your swordtails. A properly arranged tank provides ample swimming space and hiding spots when needed, without encouraging constant hiding.
  • Regularly Monitor Health: Keep a close eye on your swordtail fish for any signs of illness or distress. By proactively addressing diseases or parasites, you can prevent hiding behaviors driven by health issues.
  • Choose Compatible Tank Mates: Select tank mates with similar water preferences and non-aggressive temperaments. This fosters a peaceful environment where your swordtail fish can socialize and swim freely without fear of harassment or harm.
  • Maintain Appropriate Male to Female Ratio: Aim for a ratio of two or three female swordtails per male to reduce the pressure on females and minimize hiding behaviors induced by persistent mating attempts.
  • Monitor Water Quality: Regularly test and adjust water parameters to maintain optimal conditions for your swordtail fish. Keep ammonia, nitrite and nitrate levels in check, and ensure the pH remains stable.
  • Create a Stress-Free Environment: Minimize potential stressors like sudden movements, loud noises, or bright lights in the vicinity of your aquarium. Give your swordtails a serene atmosphere to thrive in with minimal disruptions.
  • Acclimate New Fish Properly: When introducing new swordtails to the tank, follow proper acclimation procedures to minimize stress and ease their transition into a new environment.

By implementing these preventive measures, you can create a comfortable and secure environment for your swordtail fish, ultimately reducing the need for them to hide. As a result, you’ll get to enjoy their beauty and unique behaviors as they swim around your aquarium without fear or stress.


Understanding and addressing the unique needs of your swordtail fish can pave the way for a stress-free environment, putting an end to excessive hiding behavior. We hope these tips have been helpful. Don’t hesitate to share your experiences or ask questions in the comments below!

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