Fish Laying on Bottom of Tank: Common Causes and Solutions

by | Articles, Blog, Brackish Fish, Freshwater Fish, Saltwater Fish

1.     Introduction

Sometimes fish laying on the tank bottom is a really bad thing; Other times, it’s just a regular behavior for that fish. But how can you tell the difference?

We’ll run through the most common reasons for fish laying on the tank bottom, both good and bad. Some fish may be perfectly healthy, but prefer to stay near the bottom because they’re bottom feeders (freshwater fish like loaches are common examples). Some fish may go down there to rest, or because they’re new to the tank and need time to adjust.

Other times, a fish lying on the bottom might be because it’s sick, or aggressive or territorial fish may bully shy tank mates, causing them to seek refuge at the bottom of the tank. Poor water conditions, unfavorable water parameters, and illness are other reasons a fish may be staying near the bottom. We’ll go through these in detail below.

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2. Non-concerning Explanations for a Fish Laying on Bottom of Tank


Before we get to the scary reasons for a fish lying at the bottom, let’s start by making sure there’s nothing normal about it first. Below are the most common, non-concerning reasons that your fish may be laying at the bottom of the tank. They range from old age to normal fish species behavior. It’s not always cause for alarm (although sometimes it is; We’ll get to that soon!)

2.1 Sleeping Fish


Animals and fish need to sleep, just like humans do. This is how they rest and get their energy back, just like us. Fish sleep for between 8-10 hours per day, although much of that is intermittent (sleep for 20 mins, wake for 30 mins, sleep for 15 mins, wake for 25 mins, etc.) Unless they’re nocturnal (awake at night), your fish will sleep at night when you turn off the lights. They don’t have eyelids, so they depend on the dark to rest.

Fish may be down at the bottom of the tank to rest and/or sleep. During this time, you’ll see that they keep to themselves and are much less active.

While sleeping, fish laying on bottom of tank don’t react to things going on in their surroundings. During this time, you can notice the slight movement of fish tails and rapid gill movements which tells us about their calmness and slow breathing.

You should keep lighting appropriate for the kind of fish you have. If your fish are diurnal (awake during the day), then be sure to have lights off at night so they can sleep, for example. Your fish should also have lots of decorative items like plants and nooks and crannies to hide in if they need to, since they need the dark as they don’t have eyelids. In the wild, they have access to lots of cave-like places that allow them to rest.

2.2 Newcomers


Just like other living beings, fish also take some time to adjust to a new environment. When you add a fish to your tank, it’ll take a few days for them to get familiar with their surroundings and their tank mates. During this time, they may seek refuge near the bottom.

Once they get settled with water parameters, tank mates, and the aquarium setup, you’ll see them moving all around the tank and taking part in the routine activities.

2.3 Bottom Dwellers


Some fish are bottom dwellers. They love staying at the bottom, and this kind of fish spends more time at the bottom of the tank than others do. It’s where they’d rather be. They sleep there, and they also browse the substrate looking for snacks. Bottom dwellers will naturally hang out around plants at the tank bottom.

Bottom dwellers are – as you might have guessed – bottom feeders, which means that in nature, the bottom is where they find their food, and where they’re wired to be.



Bristlenose pleco bottom dweller


Cory catfish, Kuhli loach, zebra loach, crayfish and catfish are some examples of bottom dwellers.

2.4 Elder Fish


I think fish also exhibit human behavior in this one. Humans become less active as they grow older, and so do fish.

Many aquarium fish (though certainly not all!) have a tank lifespan of about 3-5 years. When you first add them to the tank, they seem very active and roam all around the tank searching for finding their food and enjoying their life activities. But as time passes, you’ll observe them slowing down, and this can cause them to stay at the bottom of the tank.

2.5 Pregnant Fish


When a fish is about to give birth, she’ll avoid being surrounded by other fish. Instead, she’ll start finding hiding places that allow her rest, and a calm environment. This can cause a fish to be hanging out on the tank bottom.

3. Concerning Explanations for a Fish Laying at the Bottom of the Tank

3.1 Aggressive Tank Mates


If an aggressive or semi-aggressive fish is placed with a peaceful fish, the peaceful one will seek shelter from its bully tank mate. There can also be disputes or shy fish among reasonably compatible fish. Aggressive fish can chase, bully, and otherwise intimidate a more peaceful fish, causing them to look for hiding spots. They may go to the tank bottom to get out of the bully’s way. This puts them under stress, which is bad for their health, and also puts them at risk of injury. Observe your fish and how they interact with each other.

3.1.1 Solution

The best solution is compatible tank mates. This allows fish to be healthy and stress-free. You can try breaking up the line of sight in the tank with plants to help avoid territory disputes, and providing lots of hiding spots for shy fish. If that doesn’t help, then the bully might need to be moved to a separate tank.

3.2 Injuries & Illness


Incompatible tank mates can cause injury to the more peaceful fish. Another way fish get injured is through aquarium decorations; Avoid placing decor that has sharp edges in the tank. Some live rocks can be culprits of this, too. An injured fish may lay on the tank bottom. Illness can also cause this, which we’ll get to in section 4.

3.2.1 Solution


To avoid this issue, fish should be kept with tank mates that are compatible in temperament. Don’t place anything with sharp edges in the tank. If a fish is injured, consult with an aquatic vet.

3.3 Poor Water Conditions


Tank cleanliness is a major factor in keeping your fish active and healthy. If a fish tank isn’t adequately maintained with regular cleaning and weekly water changes and monitoring, fish can get sick, causing them to lay on the tank bottom.

Poor water conditions can also cause an ammonia spike and nitrate poisoning – Both of which can cause your fish to sit on the bottom of the tank. Ammonia in particular is very dangerous, and can cause lethargy in fish as they are slowly suffocating.

Overpopulated tanks have lowered oxygen levels, negatively impacting your fish’s health and breathing, and commonly have elevated ammonia.

Not changing your filter can contribute to deteriorating water quality. See for yourself:



Dirty aquarium filter

3.3.1 Solution


Keep a clean tank. Have a maintenance calendar. Perform frequent partial water changes (not big infrequent ones) and monitor your water quality and parameters regularly. Observe your fish’s behavior on a regular basis, so that you’ll be able to tell if they start acting differently. Use a high-quality filter that’s sized appropriately for your tank, and add live plants to support oxygen levels.

3.4 Inadequate Water Parameters


Fluctuating or inadequate water parameters, such as fluctuating temperature or pH, can cause a fish to hang out near the bottom. Unstable parameters cause stress to the fish, which can throw them off kilter, and cause illness. Accurate water parameters are necessary for your fish to remain healthy.

3.4.1 Solution


This one’s pretty self-explanatory:) Keep your fish tank at the correct parameters for the species of fish you’re keeping! Monitor your tank temperature. Note that temperature is particularly important for tropical fish, and that temperature can affect the good bacteria that your tank needs for healthy cycling.

4. Diseases That Can Cause Fish to Lay at the Bottom of the Tank


Just like humans, fish are less active when they’re sick. This is one reason you might find your fish laying on the tank bottom. If you suspect your fish is sick, I recommend moving it to a quarantine tank or hospital tank, for better observation and treatment, and to help prevent other fish from getting sick, too.

Problems like white spots, physical injuries, infection and ammonia poisoning can cause fish to lay on the tank’s bottom. When in doubt, consult an aquatic vet.



Medical symbol



Here are some of the most common illnesses that can cause your fish to be sticking around the bottom of the tank:

4.1 Swim Bladder Infection


In a swim bladder infection, fish suffer from gas-filled-organ. This infection will result in improper or less functioning of the bladder.

a. Symptoms


Swim bladder disease results in swimming problems. Fish suffering from swim bladder disease will either float on the top or keep themselves on the bottom of the tank. This disease can also cause a fish to swim or float upside-down.

b. Causes


The combination of overfeeding and constipation can contribute to a swim bladder infection. Dirty aquarium water is also a common cause. If your fish is suffering from other infections like kidney faults, bacterial infections, or embryo problems of female fish, then they’re more likely to develop swim bladder infections.

c. Treatment



In the case of poor water quality, regular scheduled maintenance, partial water changes, and water quality testing are necessary.

If your fish is suffering from constipation, provide them with fibrous foods. If overfeeding is at play, it may be helpful to stop feeding your fish for 24-48 hours.

A salt bath (1 tbsp salt for a 3-gallon hospital tank) can be helpful for bacterial infections, but I recommend consulting with an aquatic vet directly.

4.2 White spot disease


Ich is another name for white spot disease. It’s infectious and is a result of parasites in aquarium water. This infection hits the body of your fish and creates breathing issues in the fish. As a result of these breathing issues, the fish’s immune system will be weakened, and they may prefer to lay on the tank bottom.

a. Symptoms


If your fish is suffering from ich, then you’ll see little white spots on their skin. You may also see them rubbing against a rough surface, swimming inconsistently, or breathing heavily.

b. Causes


Ich is often caused by a sudden increase or decrease in aquarium water temperature. Poor diet and stress results in weakening the immune system of fish, which also causes ich. Another common culprit is adding a new fish to a tank without quarantining them first; They can introduce ich to your tank.

c. Treatment


The best treatment for ich is medication such as Ich-X, dosed according to its instructions. Keep your fish in a separate tank for 2 weeks while treating. While Ich-X is the most effective, here are some other common methods:

– Adding salt to a hospital tank (although you shouldn’t do this with species that are sensitive to salinity changes, like loaches).

– Formalin, methylene blue and copper sulphate.

– Giving your fish a potassium permanganate bath

4.3 Visible Injuries


If your fish is not moving actively and is instead laying on the tank bottom, it might be physically injured. Look closely for any visible wounds on the body, face, fins, or tail. These might be hard to see.

a. Symptoms


Wounds on the body, or injured fins or tails make a fish slower and less active. It may also affect their appetite, causing them to eat less or be less interested in food.

b. Causes


Causes of physical injury to a fish in an aquarium include aggressive tank mates or tank bullies, high water flow, and tank decorations, rocks, or substrates with sharp edges.

c. Treatment


To avoid this, place your fish with compatible tank mates and adjust the flow of your tank’s filter to the appropriate flow for the species you’re keeping. Remove any objects with sharp edges from the tank. If your fish is injured, move it to a separate hospital tank and treat it with antibacterial medication to prevent infection.

4.4 Ammonia Toxicity

Water testing



The presence of ammonia in your tank is fatal. It’s extremely dangerous for the life of your fish – So as a fish guardian, you need to always keep it at 0 ppm.

a. Symptoms


When exposed to ammonia, a fish may have decreased appetite. Because ammonia damages the fish’s internal organs, their activity levels may decrease. You may also see redness around their gills, which is the result of burning organs or gills (“ammonia burn”).

If you see your fish coming to the surface of the tank frequently to breathe, or laying on the tank bottom, then it can be another sign of ammonia in your tank.

You may also notice a foul smell in the aquarium – Kind of like cat pee. If you notice any of these symptoms, test your water for ammonia immediately.

b. Causes


Ammonia can be caused by a variety of things: Overfeeding, not cycling a new tank/new tank syndrome, leaving dead or decaying organic matter (uneaten fish food, dead plants, plant leaves, dead fish) in the tank, drastic water changes that remove beneficial bacteria (which keeps ammonia in check), and overstocking (causing an increase in fish waste), to name a few.

Increased pH level is another cause of ammonia levels in a fish tank.

c. Treatment


Ammonia isn’t something to wait around on: It needs to be fixed immediately, or it will kill your fish. Perform partial water changes (up to 50%) every 24 hours until your ammonia levels are at 0 ppm. Depending on the severity of the ammonia spike, you may also benefit from using SeaChem Prime to help get the levels down. Test the water every time you make a change, so you can see the effect it had on the tank before proceeding.

Remove any dead plants, fish, or uneaten food from the tank. Don’t overfeed or overstock your tank, and perform regular weekly partial water changes and maintenance. Give a new tank a boost in beneficial bacteria by adding substrate from a healthy, established tank.

Avoid pH fluctuation or high pH levels. Add driftwood (boiled first) or aquarium-safe peat moss to the aquarium to lower pH levels as needed.

5. FAQs



X-ray tetra

5.1 Would Wrong Water Parameters Cause My Fish to Hang at the Bottom of the Tank?


Short answer: Yes. Tank temperature and pH in particular can stress out your fish, throw them off kilter, and cause illness, making them want to hang out at the bottom of the tank.

5.2 Why isn’t My Betta Fish Moving?


If your betta fish isn’t moving, but is still breathing, it may be suffering from swim bladder disease. To be fair, your fish could be suffering from other causes on this list; You will have to work through any other symptoms and test your water to get the whole picture. It’s also worth mentioning that bettas aren’t very active fish in general, so if you’re new to keeping them, bear this in mind. I’d encourage you to consult with an aquatic vet if you’re concerned about your betta fish laying at the bottom and/or not moving.

5.3 What Does It Mean When Your Fish Is Laying On the Bottom?


If your fish is laying at the bottom of the tank and it’s not a bottom feeder or elderly fish, then it may be sleeping, resting due to pregnancy, injured or maybe suffering from different diseases like ich, or swim bladder disease.

5.4 What to Do If Your Fish Is Sitting at the Bottom of the Tank?


What you do depends on why your fish is sitting at the bottom of the tank. If it’s due to a stressful tank mate, the bully may need to be removed. If it’s due to disease or illness, you will need to move your fish to a hospital tank and treat it accordingly. If it’s because of poor water quality, you’ll need to perform partial changes and clean your tank until it’s up to par.

5.5  Why Is My Fish Not Moving at the Bottom of the Tank?


If your fish isn’t moving at the bottom of the tank, then it may be sleeping or suffering from disease. Please make sure your fish is still breathing, and consult an aquatic vet if you’re unable to find a solution from this post.

6. Conclusion


Keeping pet fish is a big responsibility. Maintaining accurate water parameters, good water quality, and following best practices like quarantining a new fish before introducing it to your tank are all steps you can take to keep your fish healthy. Observe your fish for any changes from normal behavior.

It’s common for sick fish to be laying on the tank bottom. That said, there are also some instances in which it’s normal for fish to be there – Like bottom feeders. Use your own good judgment, and err on the side of caution for the sake of your fish. If you’re not sure, talk to a vet!

Keeping an eye on all the signs and causes will help you in saving your fish’s life.



Additional Sources/Resources/Reading



To say that I’m obsessed with all things saltwater is a bit of an understatement. Aquarium Passion has served freshwater and saltwater aquarium hobbyists for over 10 years, and I'm committed to keeping the information accurate and free. My post-bac certification in Sustainability informs my writing about aquarium conservation efforts. When I'm not writing at AP, I'm out in the ocean or researching weird fish.


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