Why is my Swordtail Laying on the Bottom?

I got quite worried about seeing my swordtail laying on the bottom often, so I decided to find out the cause. Today, I am going to share all my knowledge with you that I learned in this regard.

Why does a swordtail prefer to lie on the bottom of the tank? One reason could be that the fish is under stress due to some disease or improper tank conditions. Stress can also be caused if other tankmates are bullying the fish. Pregnant swordtails might also prefer to stay low.

It is essential to be aware of the causes that prompt the swordtail to lie on the bottom so that the right measures can be taken for its betterment

What causes the swordtail to lie on the bottom?

When one is setting up an aquarium, swordtail fish are among the first choices that he opts for to populate the tank. Swordtail fish are beautiful and peaceful species along with being social and active. However, sometimes, you will find that one of your swordtails is simply lying on the bottom, without any significant movement. This can be very alarming as it could be a sign that the fish is unwell. Therefore, finding the cause to this behavior is very important.

The two main reasons which lead to swordtails lying on the bottom include:

  • Stress
  • Pregnancy


One of the leading causes of the swordtail lying low is that they are under some stress. The following two conditions could cause stress for a swordtail fish.

Tank conditions

Swordtails are large fish and thus need the right size of tank to thrive. The minimum tank size for a swordtail is 15 gallons and if you intend to have more of these fish, increase the capacity to up to 30 gallons so that the swordtails have adequate room for movement.

Drastic changes in water temperature can also stress the fish. Keep the temperature between 72- and 78-degrees Fahrenheit and keep a close check on the water conditions. Change 25% of the tank water every week. The pH should be kept between 6.8-8 with water hardness from 1DH to 24DH.


Sometimes, a fish is bullied by its tankmates who place it under a great deal of stress, and thus it prefers to lie at the bottom to avoid the company. Take a close look at the behavior of the other fish to determine which one is the bully and remove it from the tank. Maintaining male to female ratio of 1:2 or 1:3 is advisable.


Pregnancy could be another reason why your swordtail might be swimming close to the bottom. During breeding, swordtail fish tend to lie in solitude and restrict movement. Make sure that the swordtail is adequately fed during this period. There is not much that you need to worry about in this case as this is completely natural. Just make sure that the mother swordtail is back to full health and swimming normally after she gives birth.

Can diet be a reason for lethargy in swordtails?

It is not very common for swordtails to become lethargic or unwell due to diet. This is because swordtails are not very particular about their food. As long as you give them the right mix of protein and other nutrients, they will thrive. You can give them artificial food as well but make sure that it is of optimal quality and does not contain any ingredient which can incur harm to the fish. Vegetable supplements should also be provided to them. Every now and then you can also treat them with live food.

The pregnant swordtails should be given sufficient meals; otherwise, it might end up eating its fry as soon as they are born. When it is close to giving birth, the mother swordtail should be given meals twice a day as this would reduce stress induced by hunger.

What are the other consequences of stress in swordtails?

Apart from lethargy, swordtails that are under stress also have a higher chance of being affected by ich. Ich is among the most common illness found in aquariums, and thus one needs to be aware of the signs. It is an external parasite. However, the parasite is usually unable to infect healthy fish. Therefore, if you find a fish suffering from ich, you need to understand that it is probably under some stress.

Ich causes white spots on the body of fish which resemble salt grains. The primary treatment of the condition is to remove the stress factor and to change the water of the tank. Once you deal with whatever is causing stress to the fish, it will not take long to return to its healthy state. You can also opt for salt treatment. The appropriate dose is one tablespoon for every five gallons of water. However, put half dose first and then another dose after 12 hours to avoid any reactions. Garlic is also found to be effective.

Does ammonia poisoning cause swordtails to lie low?

Ammonia poisoning could very well be a reason why your swordtails are laying low. If swordtails are exposed to high levels of ammonia for a long time, they can eventually succumb to death. The first sign of ammonia poisoning is gasping. You will find the fish struggling to breathe. Some changes on its body will also start to appear, and gradually it will become lethargic. If appropriate measures are not taken at this point, organ damage commences. The fish begins to bleed externally and internally before ultimately breathing its last.

In order to treat ammonia poisoning, do frequent water changes in your aquarium and take out any organic matter that might be lying inside the tank. Also, you should reduce the frequency of feeding your fish as the excess fish flakes or any other type of food over time decays into ammonia.

How To Breed + Care for Swordtails (Video)

Related questions

Do tank decorations affect the swordtail in any way? The way your tank is decorated is indeed significant for swordtails. For one thing, you need to keep it thickly planted, particularly at the bottom. This ensures that the stressed and pregnant fish have some place to bide their time. Furthermore, you need to avoid using sharp stones and pebbles for decorating the tank as this can seriously injure the fish

How can I tell if my swordtail is pregnant? The gestation period of a swordtail is around 28 days. However, determining when the fish became pregnant is not easy. For this, the female body needs to be examined carefully.

The belly starts to protrude which is a clear sign of pregnancy. The abdomen soon appears somewhat square shaped as the time of spawning grows near. You will notice a dark spot near the anus on either side of her body which is called the gravid spot. This should tell you that the time of birth is approaching and that you should take the required measures to protect the fry before its parents or adult tankmates eat it.

Should I separate the pregnant swordtail from the other fish?  Separating the pregnant swordtail from other fish as it approaches spawning will indeed prove beneficial. For one thing, it will get the opportunity to lie in solitude and will not have to face any competition for food, thereby reducing stress on it. Furthermore, you will be in a better position to protect the fry if it is born in a separate tank. A special depositing hopper can be used. This way, the fry fall into a spawning tank soon after birth which protects them from the adults.


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