Why Did My Pleco Die? (With 7 Prevention Tips)

Disclosure: When you purchase something through my affiliate links, I earn a small commission. As an Amazon Associate, I earn from qualifying purchases.

Like many aquarists, I get disappointed when I find dead fish in my tank. For example, there were times when I found that my pleco suddenly died, even with my best efforts to prevent this.

Over the years, I’ve learned a few lessons on that matter. After I know how to stop it from happening, I am willing to share my experience.

Plecos usually die due to inadequate water conditions, including ammonia spikes, temperature fluctuations, and salted water.

However, sudden death in plecos may also be due to starvation, inappropriately cycled tanks, bullying tankmates, diseases, and overcrowding, particularly in small tanks.

As we move forward, I will share a few other reasons that might have killed your pleco fish. Then, I will list seven tricks that will help you to prevent this from happening again. I will also show you how to treat a dying pleco and possibly save it from a cruel fate.

Also Read: Pleco Fish Facts

Why Do Plecos Die?

If your plecos are suddenly dying, you need to find out why. It isn’t normal for a pleco to drop dead. And if yours are doing just that, there are some factors to blame.

Even if you are convinced that your pleco’s death is natural, you are still encouraged to investigate the following factors:

1. The Pleco Was Carrying a Defect

Some plecos are sick by the time they arrive from the fish store. If they are not diseased, they possibly came from a bad batch tainted by genetic complications.

Such plecos will die soon after arriving in your aquarium because they are too sick to survive the stress induced by the transition.

2. The Aquarium Was Too Salty

A lot of aquarists use aquarium salt since it has a calming effect that stressed fish appreciate. You can also use it to aid the healing process in sick fish.[1] However, plecos do not like aquarium salt. 

It isn’t just a source of discomfort. Aquarium salt can kill your plecos by not only burning their gills but also dehydrating them. If you have a habit of adding salt to your aquarium, your pleco’s death shouldn’t surprise you.

3. Your Pleco Didn’t Get Enough Food

Plecos are algae eaters, and some buy them for this very reason. However, it would help if you didn’t assume that your plecos can survive solely on the algae in the tank.[2]

The algae will contribute to their regular meals. However, many plecos are omnivores that eat smaller fish all the time.

But even if your plecos only eat plant matter, you are still expected to feed them. Some aquarists do not know this. They assume that their plecos will survive on the algae in the tank, which is why they make no effort to feed them. As a result, their plecos starve to death.

4. The Pleco Was Exposed to Ammonia

Like all aquarium fish, plecos cannot stand ammonia and nitrites. You have to keep their concentrations at zero.[3] Otherwise, they will harm your plecos, not only burning their gills and compromising their ability to breathe but also inducing stress and making them vulnerable to diseases. 

High levels of ammonia and nitrites will kill your plecos if you fail to take immediate action.

That usually happens in dirty tanks that have accumulated a fair amount of leftovers and debris. When rotten food decays, it releases ammonia and nitrates.

5. The Tank Wasn’t Properly Cycled

Was your tank properly cycled? The cycling process, which takes weeks, introduces bacteria that remove waste and toxins like ammonia and nitrites.[4] If you add plecos to your tank before it is adequately cycled, the fish will eventually die.

If your tank is cycled, but the plecos are still dying, you should test for chlorine. Chlorine will kill the good bacteria that the cycling process produces. That typically occurs in tanks that contain tap water with high chloramine concentrations.

6. Your Fish Suffered From Inadequate Water Conditions

Plecos require specific parameters in their water. You are encouraged to replicate the conditions to which they are accustomed in the wild. That means making sure that the pH, temperature, hardness, and tank size are correct.

The wrong parameters will make your pleco sick, and if these parameters persist, the fish will eventually die. The wrong parameters include fluctuating temperatures, water that is either too hard or too soft, and small, overcrowded tanks.

7. The Pleco Was Consistently Stressed

Stress is one of the most common causes of unexpected death in fish. Plecos are large, but they are not immune to stress.

Stress can be caused by extreme temperatures, fluctuating temperatures, the wrong pH, the presence of aggressive tankmates, underfeeding, disease, and so much more.

Common symptoms of stress include incessant hiding, glass surfing, color fading, and weight loss. Generally, stressed plecos are also more vulnerable to diseases. These, in the long term, can kill your fish.

Also Read: Stress In Pleco Fish

8. The Fish Was Overfed

Some people feed their plecos every day, while others feed them every other day. Regardless of the schedule you choose, overfeeding is discouraged. First of all, it will increase the waste the plecos produce.

That will introduce toxins that will ultimately kill the pleco. If they survive the ordeal, overfeeding can lead to constipation and swim bladder disease. In that case, before the pleco dies, you’ll see that it lies on its back at the bottom of the tank.

9. Your Pleco Was Sick

Fish get sick all the time. Like humans, a pleco will die if its illness isn’t treated. Common pleco diseases include Ich, Dropsy, Fin Rot, and Hole in the Head, to mention but a few.[5]

Even though common plecos are large fish, you should know that a disease can weaken them to the point of making them vulnerable to smaller fish.

The creature’s size won’t always protect it from its tankmates. A sick, listless, lethargic pleco cannot defend itself. In this case, you’ll notice bullying tankmates taking advantage of the weakened fish, consistently nibbling and harassing it.

How to Prevent Plecos From Dying?

Unless your pleco is merely old or genetically defective, there are several steps that you can take to protect it from unnecessary deaths, including:

1. Adjusting the Temperature, pH, and Alkalinity

I highly suggest that you maintain the right parameters in your pleco tank. That includes a pH of 7.0-8.0, a temperature of 74 to 80 degrees F, and alkalinity of 3 to 10dKH.[6] You can only maintain these parameters by testing the water regularly.

That is where I highly recommend checking the API Aquarium Test Kit (link to Amazon). That bundle will accurately measure your pH, nitrates, nitrites, and ammonia. Within minutes, you will know if something has gone wrong.

If your heater is malfunctioning, you should definitely consider the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon). After testing multiple heaters, I can confidently say that this is the one you should get.

Also Read: Plecos Water Parameters

2. Getting a Tank of at Least 50 Gallons

Many aquarists house plecos in small tanks, although the creatures require tanks of 50 to 100 gallons. This is because they have an average size of 24 inches.

However, many aquarists get plecos when they are young. And unfortunately, during these early stages, they are relatively small.

This is why you are encouraged to base your choice of a tank on the size the pleco will achieve when it reaches adulthood.

Get a tank that can accommodate plecos once they mature. Try not to focus on the juveniles’ size; it will deceive you.

Also Read: Pleco Fish Tank Size

3. Feeding the Plecos Daily

Because plecos eat the algae in a tank, you don’t have to feed them twice a day, every single day like other fish. As was noted before, you can feed them once a day or once every two days. Regardless of the schedule, it would be best if you fed them.

Please do not assume that they can survive on the algae in the tank. Once you craft a schedule, maintain it. If you find it difficult, I highly recommend getting the Eheim Automatic Feeding Unit (link to Amazon). Merely set the feeding schedule and let the device do its trick.

Also Read: How To Feed Plecos

4. Acclimatizing Plecos to Their New Tank

Take the time to acclimate new plecos. Gradually introduce them to the pH and temperature of their new tank.[7] This will prevent unnecessary stress. Sudden transitions can shock new fish, creating timid personalities. 

You can avoid this by adequately acclimating your plecos. The easiest way would be to submerge the plastic bag from the store inside the tank for one hour. That will create a balance in terms of temperature, which is the most crucial factor in the process.

5. Putting Sick Plecos in Quarantine

Whenever your pleco falls seriously sick, you should place it in quarantine. The objective isn’t to prevent the pleco from infecting the other fish in the community tank. By isolating the sick pleco, you are making it less vulnerable to attack during its weakest moments. 

Quarantine also offers peace, especially for plecos with aggressive tankmates. The quarantine allows the plecos to recover in a tranquil environment.

This also enables you to treat the entire tank with the relevant chemical products without affecting the pleco’s tankmates.

If you suspect that your fish is sick (they usually seem lethargic and become pale), put the pleco in quarantine and seek an expert. Aquatic vets can quickly diagnose the underlying condition and adjust the treatment accordingly.

Also Read: Pleco Fish Diseases

6. Choosing the Right Tankmates

Speaking of tankmates, you need to pair the pleco with compatible fish that won’t antagonize it. That includes Hatchets, Arowanas, Danios, and Gouramis, to mention but a few.[8]

Avoid fish that are large enough to prey on the plecos. The plecos are just as likely to get lodged in their throats, which won’t do them any good.

Also Read: Pleco Fish Tank Mates

7. Maintaining a Clean Tank

I highly suggest that you keep the tank clean. You can do this by performing regular water changes, installing efficient filters, vacuuming the substrate, and removing dead organic matter before it rots. Dirty water weakens the fish’s immunity in the tank, exposing them to illnesses that can kill them.

Of course, no amount of maintenance can protect your fish if your tank isn’t cycled. Proper cycling takes weeks.

Take as much time as you need to prepare the aquarium before you add the plecos. Otherwise, the poor conditions in the tank will kill them.

How do You Save a Dying Pleco?

Saving a dying pleco involves these steps:

  1. Move the fish to a hospital tank using a gentle net.
  2. Install a heater and a filter to create aeration.
  3. Adjust the temperature to 74 to 80 degrees F.
  4. Measure the pH and ensure that it doesn’t go lower than 7.0.
  5. Perform regular water changes, especially during ammonia spikes.
  6. Consult an aquatic veterinarian if the fish appears ill.

Preventative measures are supposed to keep your plecos from situations that might lead to death. But if your fish is already at death’s door, don’t be so quick to abandon it.

There are steps that you can take to save the creature’s life during emergencies. Consider the following:

1. Getting the Right Tools

Every aquarist should keep an emergency tool kit on hand just in case things go wrong. In the absence of such a tool kit, your pleco is more likely to die.

Before the worst comes to pass, you should take a moment to assemble all the tools you may need in an emergency. That includes:

  • Filters and Pumps – Keep some air pumps and sponge filters on hand. Sponge filters are popular because they are cheap and easy to use. They are also easy to clean. If your primary filter stops working, a sponge filter will stand in the gap until a replacement arrives. The same goes for an air pump.
  • Tank – You need an extra tank that can house quarantined fish. It doesn’t have to be as large as the main tank. But it should be large enough to house one or more plecos.
  • Heater – Like the filter and air pump, your heater can malfunction. To protect your plecos from the sort of extreme temperatures and fluctuations that may lead to death, you need an extra heater. You should get a spare heater for your quarantine tank as well.
  • Testing kit – This goes without saying. Every aquarist needs a testing kit since this is the only way to monitor the ammonia, nitrate, nitrite, and pH levels.
  • Net – A lot of fish die because they are handled poorly. This is why every aquarist needs a fishing net. If your fish is close to death, then the stress of poor handling will make things worse. A gentle net allows you to move a sick fish without hurting it.

2. Quarantine the Dying Pleco

If your fish is very ill, you should place it in quarantine immediately. This will protect the creature from fish that may attempt to take advantage of its weak state by attacking it.

The hospital tank doesn’t have to be that large since it only accumulates one fish.

3. Create Aeration in the Hospital Tank

If an oxygen deficiency is the cause of your pleco’s dire situation, you can improve aeration immediately by agitating the water. You can do this by stirring it or pouring new water into the aquarium from a great height.

Not only will this agitate the old water in the tank, but the new water will collect oxygen as it falls through the air. This will add the necessary oxygen to the tank. These steps are just emergency measures that will keep your fish alive until you acquire a permanent solution.

4. Adjust the Temperature

High temperatures can reduce the oxygen in the water, causing the fish to suffocate. You can reduce the tank’s temperature quickly and easily by switching the heater off, turning the lights off, and moving the aquarium away from direct sunlight. 

You can even use a fan to blow across the surface of the water. In the worst-case scenarios, you can add some ice cubes in zip-close bags. Some people use hydrogen peroxide in extreme situations.[9] Either way, make sure that the temperature stays between 74 to 80 degrees F.

5. Take Care of pH and Toxins

If the pH is falling too quickly and drastically, you can use sodium bicarbonate. The substance acts as a buffer and will keep the pH from slipping further. But it is best to prevent this from happening in the first place. Therefore, make sure that you carry regular water changes and remove debris and leftovers.

If your plecos are dying because of a spike in toxins like ammonia and chlorine, add a water conditioner. Water conditioners will neutralize these toxins in minutes, preventing them from doing any additional damage.[10]

Also Read: Signs Your Pleco Fish Is Dying

Do Plecos Float When They Die?

Plecos float when they die because, like most fish, dead plecos hold trapped gas inside their bodies. Since they cannot extract it properly, the gas will move them upwards. However, as it dissipates, the dead pleco will gradually sink to the bottom.

If your pleco is floating at the top without moving, it is probably dead. At this point, you can remove the fish away from the tank.

You can catch this case in time by observing the fish. If you notice worrying signs such as sluggish behavior and color changes, move the fish to quarantine and consult an aquatic vet.

Also Read: Why Did My Pleco Disappear?


If you find your pleco dead, there are a few steps you should take. First, you should create a suitable environment for plecos. That includes checking the temperature and pH. I also suggest getting a testing kit to make sure an ammonia spike didn’t occur.

You should also make sure that the tank is large enough for plecos. These fish enjoy tanks of at least 50 gallons. If the aquarium is too small and crowded, your plecos will likely be bullied, which will eventually compromise their health and general state.


  1. https://www.algone.com/using-salt-in-the-freshwater-aquarium
  2. https://www.fishkeepingworld.com/plecostomus/
  3. https://www.swelluk.com/blog/why-do-my-fish-keep-dying/
  4. https://fishlab.com/why-your-fish-are-dying/
  5. https://animals.mom.com/plecostomus-diseases-6425.html
  6. https://www.aqueon.com/information/care-sheets/plecostomus
  7. https://www.thesprucepets.com/reasons-that-fish-die-in-aquariums-2925394
  8. https://www.buildyouraquarium.com/plecostomus-tank-mates/
  9. https://www.dvm360.com/view/fish-emergency-medicine-proceedings
  10. https://www.fishlore.com/aquariummagazine/jan08/aquarium-first-aid.htm