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Betta Fry At The Bottom Of The Tank: Reasons & Solutions

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Betta fish fry are incredibly delicate creatures, which is why many aquarists get worried when they see them acting strangely. For example, it is pretty prevalent for betta fry to swim at the bottom, but it immediately raises the question: why?

Newborn betta fish fry will naturally sink to the bottom of the tank as they cannot swim properly. But once they become free swimmers (days 3-7), betta fry may still stay at the bottom due to water abnormalities, such as high toxins and swinging temperatures.

As we move forward, I will elaborate on what might have caused your betta fry to swim at the bottom. Then, I’ll show you how to identify those cases in which this is an actual problem and how to get around it.

A two-day-old baby betta fish, hanging vertically.

Still curious? Feel free to check my complete guide on betta fish fry, where I discussed how to care for betta fry, what they eat, their growth stages, what equipment to use, and much more.

Why Do Betta Fry Stay At The Bottom Of The Tank?

Bottom dwellers like Plecostomus, Kuhli Loaches, and Corydoras catfish are aptly named. They spend a lot of time at the bottom of the tank.[1]

But betta fish are not bottom dwellers. As such, no one will blame you for acting concerned if their offspring are swimming or lying still at the bottom of the tank. 

Fortunately, this behavior has a rational explanation:

1. Newly Born Betta Fish Fry

Betta fish do not swim at the bottom. They tend to frequent the middle sections of the tank. Therefore, you shouldn’t expect betta fry to stay at the bottom either.

But that doesn’t mean this behavior is always a sign of trouble. You should first ask yourself one central question: how old are the fry?

Baby bettas start their lives as eggs. They have to transition through the fry, free-swimming, and juvenile stages before attaining sexual maturity.[2] I explained this more in detail here.

The male betta will protect them during the egg stage, returning the creatures to the bubble nest whenever they fall out. 

The father will continue to perform this role even after the eggs hatch because the fry cannot swim. They will continuously sink to the bottom of the tank for the first two days. 

If you take the male fish out of the breeding tank, the fry will stay at the bottom until they reach the free-swimming stage, where they can move horizontally through the water.

If your baby betta’s tail is hanging downward, it hasn’t reached the free-swimming stage. Therefore, the fry’s presence at the bottom shouldn’t concern you.

Betta fry with tails hanging downward; still not free swimmers.

2. Older Betta Fish Fry

You cannot always blame your betta fry’s behavior on their age. If the creatures have entered the free-swimming stage but continue to frequent the bottom, investigate the following factors:

  • Food

It is not enough to change the water in an aquarium. Typically, you should vacuum the substrate because all the food you add to the water will eventually settle at the bottom. 

Some betta fry swim at the bottom because they are looking for food. You cannot rule out food as a contributing factor simply because you can’t see any food on the substrate. 

Betta fry will eat microscopic foods like infusoria for the first few days. You cannot see these tiny foods with the naked eye. Young fry eat them precisely because they are small enough to fit in the mouths of the baby bettas. 

  • Toxins

Test the water for toxins. Ammonia will sap a baby betta’s strength, forcing the fry to the bottom. Fry are less likely to survive high concentrations of toxins.

Ammonia is not your only concern. You may inadvertently introduce substances like chlorine and lead to the water during a water change. 

Fish typically respond to toxins with stress, and one of the most common symptoms of stress is swimming at the bottom of the tank. That applies to both fry and adult fish.

  • Filter

Filters create two primary complications. If they are too strong, the filters will generate powerful currents that induce stress in the fry. The exhausted fry will hang out at the bottom.

If the filter is too weak, oxygen deficiencies will form in the aquarium. Yes, bettas have labyrinth organs that can extract oxygen from the air. The organs allow adult bettas to survive in shallow water.[3]

But it can take up to six weeks for betta fry to develop a labyrinth organ.[4] You cannot expect them to thrive in oxygen-deficient environments. 

  • Temperature

Betta fry do not appreciate extreme temperatures. Besides reducing the oxygen concentration, extreme temperatures (high or low) will overwhelm the fry with stress, exposing them to dangerous diseases. They will gasp for breath at the bottom before dying.

  • Swim Bladder Disease

Swim bladder disease can affect a fry’s ability to swim. It will slide along the bottom because the sick or damaged swim bladder won’t let it ascend. The fish is essentially grounded until it recovers.

Fry do not always recover from swim bladder disease. Some of them are forced to tolerate permanent deformities for the rest of their lives.

If the entire batch of betta fry is swimming at the bottom, it is more likely due to the aforementioned environmental factors. 

But if a single fry stays at the bottom and seems swollen, swim bladder disease is a valid explanation.

Three-week-old fish betta fry that are currently free swimmers.

What Should I Do If My Betta Fry Swim At The Bottom?

You don’t have to leave the fry at the bottom to their fate. You can use the following steps to aid them:

1. Look For Troubling Symptoms

Don’t take any drastic steps until you observe troubling symptoms such as losing appetite and lethargy. Some fish are sleeping, while others merely prefer the bottom.

Don’t blame this behavior on diseases and extreme temperatures unless you notice concerning signs. Leave the baby bettas alone.

2. Maintain Proper Water Conditions

Aim for these water parameters when it comes to betta fry: 

  • Temperature: 85-88° F (29-31° C) 
  • pH: 7.0-7.2 
  • General hardness: 2-20 dGH (70-300 ppm) 
  • Carbonate hardness: 3-5 dKH (55- 90 ppm) 
  • Ammonia: 0 ppm 
  • Nitrites: 0 ppm
  • Nitrates: <20 ppm

To measure the pH, ammonia, nitrates, and nitrties, I personally use the API FRESHWATER MASTER TEST KIT (link to Amazon). This kit is highly accurate and lasts for eight hundred measures.

As for the water hardness, you can simply go with the API GH & KH TEST KIT (link to Amazon). It is pretty affordable and easy to use.

If the parameters are wrong, alter them gradually. Raising or lowering the temperature suddenly will do more harm than good. Fish don’t appreciate drastic fluctuations.

This is why new aquarists are encouraged to perform small water changes every week. A large water change will harm the baby bettas. If the ammonia concentration is too high, it is even better to use conditioners. 

They will neutralize the ammonia, allowing you to perform small water changes that can improve the conditions in the aquarium without shocking the babies.

I typically use the well-known Seachem Prime (link to Amazon). But frankly, most water conditioners on the market will get the job done.

3. Feed Your Betta Fry Properly

A nutritious diet will allow sick bettas to recover quickly. Baby bettas require a protein-rich diet. Give them live foods such as micro worms, baby brine shrimp, and vinegar eels.

For your convenience, here is a table that shows you what betta fry need to eat depending on their age (you can find more information in my complete betta fry feeding guide):

InfusoriaUntil they reach day 7
Baby brine shrimpFrom day 7 to 21
Freeze-dried/frozen foodsFrom day 21 and beyond
BlackwormsFrom week five and beyond
Dry pelletsFrom week eight and beyond

Try to feed them five or more times a day. Because frequent meals will increase the volume of leftovers, you should also install reliable sponge filters that can keep the water clean.

Some people are tempted to use stronger filters to agitate the water because they want to avoid oxygen deficiencies. But you are better off adding air stones to the tank.

4. Cull The Fish

Diseases and ailments are not a big deal among adult bettas because you can cure most of them. But an illness in a betta fry tank is dangerous because it can have lasting consequences.

The fry may develop illnesses and deformities they will never shake until they die. This is why some aquarists respond to swim bladder disease by killing the babies in question.

This solution sounds harsh, but it is actually a kindness for fry whose organs are so swollen that they can’t swim.[5]

Here is an excellent Youtube video that will show you all about it:

If you found this article helpful, these may also interest you:

Conclusions

During the first several days of their lives, betta fry will naturally sink to the bottom because they cannot swim just yet. That usually happens during their first week, as soon as they are separated from their bubble nest.

But if your betta fry are already free swimmers (day seven and beyond), you should start by identifying additional symptoms, such as lethargy and loss of appetite. That may suggest a disease.

But if the entire batch is at the bottom, the reason is more likely environmental, and you should test the water parameters. If you notice an abnormality, correct it gradually, preferably using a water conditioner.

References

  1. https://be.chewy.com/5-great-bottom-dwelling-freshwater-aquarium-fish/
  2. https://aura.alfred.edu/bitstream/handle/10829/24485/Hameister%2C%20Ava%202021.pdf?sequence=1&isAllowed=y
  3. https://pure.royalholloway.ac.uk/portal/files/28096477/JFB_RP_16_007_Author_Accepted.pdf
  4. https://drqandu.org/betta-fish-101/
  5. https://pethelpful.com/fish-aquariums/Belly-Sliding-Betta-Fish-Fry-What-Does-It-Mean