Why Is My Plecostomus Laying Upside Down? {Top 6 Reasons Explained}

Are you seeing your plecostomus upside down in your tank? Is this a sign of disease or imminent death? In this article, we’ll hope to explain the reasons as to why your pleco is laying upside down.

Why Is My Plecostomus Laying Upside Down? Swim bladder disease is the most common reason why a plecostomus would be laying upside down. Buoyancy is affected by a malfunctioning swim bladder due to disease or bloating. Sometimes it’s temporary when they are looking for food at the surface, other times it’s terminal. 

Does My Plecostomus Have Swim Bladder Disease?

Sometimes we may notice strange behavior from our marine life from the way they look, swim or remain motionless. Plecostomus, commonly referred to as plecos, have the tendency to lie upside down when something is wrong.

Your plecostomus could be suffering from swim bladder disease.  The ability to swim upright or their buoyancy becomes greatly affected. This could be due to an infection that may not be curable. Your plecostomus could survive for years with swim bladder disease.

Check to see if its intestines or stomach are enlarged. Do not feed your pleco for 3 days and look for improvements in buoyancy. You might be fortunate enough to eliminate the diagnosis of swim bladder disease.

What Causes A Plecostomus To Float Upside Down?

The most common cause for a plecostomus to float upside down is when the swim bladder is unable to control its upright swimming ability. This could turn serious or become a part of its long-term future to live with it. Six reasons for floating upside down are listed below:

  1. swallowing air
  2. constipation
  3. infection
  4. pregnancy
  5. starvation
  6. death

1. Swallowing Air

Swallowing air happens more when fish feed at the surface. This is not as common for plecostomus, but it may occur when you see them at the top of the tank. The stomach full of air can affect the swim bladder from working properly.

2. Constipation

Constipation blocks the digestion of your plecostomus. The bloating that results pushes against the swim bladder. Your pleco may not be able to be as buoyant during this time. Try to stop feeding or switch to shelled peas to help pass any impacted food.

3. Infection

Swim bladder disease is one type of infection, but there are other illnesses in play when you notice your plecostomus upside down for long periods of time. Callamanus worms causes bloating and you may see these worms protruding from the anus. Dropsy also causes bloating.

4. Pregnancy

The eggs of a female may also push against the swim bladder. This type of bloating is temporary and will not be an issue once she lays her eggs.

5. Starvation

We tend to leave our plecostomus free to roam and pursue its algae eating mission in the tank. Sometimes this fish becomes so deprived of nutrients that it may swim up to the surface upside down to look for food at the surface.

This is not as common as swim bladder disease, but it’s worth noting that we need to supplement the diet of a plecostomus with more food sources other than algae.

6. Death

Unfortunately, this is the sign of grave things to come in many cases. If you see any marine life floating upside down, you tend to think of the worst. Your plecostomus might be dying or has already passed away.

Look for signs of life with gill movement. Use a quarantine tank with ideal water parameters to see if anything changes. If this is the end, we are sorry for your loss.

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Is My Plecostomus Injured?

The swim bladder is a sensitive area in your plecostomus. It can get injured from violence or accidents. Aggression between a tankmate can result in an injury to the swim bladder. Sometimes a pleco swims full speed into a decoration, rock or against the glass that causes the swim bladder to stop functioning properly.

Observe this behavior for 2-3 days and stop feedings for now. Allow for plenty of dark hiding spots for your plecostomus to rest during this time and hope it can recover on its own.

What Should I Do When My Plecostomus Is Upside Down?

If you notice your pleco upside down for too long, something is wrong. Is there any gill movement or swimming going on? Add food, change the water or make gentle contact. If none of these suggestions trigger any response, your pleco’s condition is probably terminal.

The best-case scenario is that your pleco is bloated or pregnant. Both conditions that push against the swim bladder are temporary. Try not to overfeed during this time. Keep the water parameters ideal with the following guidelines:

  • Water Temperature: 74-80° F
  • pH: 7.0-8.0
  • Alkalinity: 3-10° dKH (54 ppm to 180 ppm)
  • Nitrates: Less than 40 ppm
  • Nitrites and Ammonia: 0 ppm

Elevate the temperature to the higher end of this range. Digestion speeds tend to increase with warmer water. A heater in your tank will make this change much easier. Adjust one degree per hour if you can to prevent sudden changes from stressing any other tankmates.

How Do Set Up A Tank For My Plecostomus?

We want to prevent swim bladder disease or prevent any other reason for your plecostomus from swimming upside down. The tank needs to be cycled and beneficial bacteria will do their best to prevent infections.

Conditioners keep chlorine, ammonia and nitrites in check. The tank size must be large enough to prevent stress and injury. A pleco that grows 15-24 inches needs a tank larger than 50 gallons.

These fish need more shaded areas. Decorations, plants, caves, logs and rocks will help keep your plecos healthy and calm. Stress brings out the worst in fish. Immune systems weaken and swim bladder disease will become more likely.

  • Healthy nitrogen cycle
  • Water Conditioner
  • pH balance of 7.0-8.0
  • Larger tank
  • More decorations
  • Heavily planted areas
  • Reduce stress from tankmates
  • More food sources other than algae


We hope your pleco doesn’t have swim bladder disease, but we believe that with the right adjustments, it can still live a long life with this condition. Floating upside down in temporary occasions is more likely due to bloating issues that press against the swim bladder of your plecostomus.

The worst of all is that your upside down pleco has passed away. We wish for better days ahead with learning curves along the way.


Thank you for stopping by at HelpUsFish.com for all your informational needs concerning the fish you wish to keep in your aquarium. We have plenty of articles on a wide variety of marine life that may also pique your interest. See you again soon!

Brian Arial

Brian Arial has kept fish for leisure and worked with fish stores for most of his life. He enjoys writing and caring for aquariums and ponds.

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