Why Do Fish Lay At The Bottom Of The Tank?

We do not understand what our aquarium fishes tell us most of the time. They have their way of communicating how they’re feeling.

Sometimes you notice some unusual behavior from your fish, which is often expected, and sometimes they need special care from you.

So, Why do fish lay at the bottom of the tank? There are plenty of reasons why fish lay at the bottom of the tank. Applying at the bottom of the tank is normal when it happens routinely.

If your fish first shows this behavior with stress or disease, you must investigate the cause.

If you have no substrate or no hiding place, in this case, fish may think the bottom is the safest place to rest. If your fish show a lack of appetite, you should pay close attention to your fish.

Find and solve The root case as soon as possible.

In this guide, we will learn why fish lay at the bottom of the tank. What are the reasons and effective measures to cure and prevent them?

Why Do Fish Lay At The Bottom Of The Tank?

There are several normal circumstances when your fishes are at the bottom of the tank like:

  • Bottom Dwellers.
  • Bottom feeders.
  • Resting Fish.
  • Older Fish.
  • New to your aquarium.
  • No hiding spots.

But also there are several circumstances where you should pay close attention like:

  • Sudan water temperature rise or drops.
  • Unstable water parameters.
  • Disease.

No hiding spots

Suppose you see a mid-level swimmer fish come and lay down at the bottom of the tank. You should closely monitor that fish, especially when it tries to move to mid-level. If it’s getting harassed by a bully or getting nipped at, there’s a tank mate incompatibility issue.

There are other reasons like:


  • Add more hiding spots.
  • Identify the bully and remove him.
  • Keep a mix of bottom dwellers, mid-levels swimmers, and surface feeders.
  • Use AqAdvisor to check if your tank is overstocked.
  • Get an additional tank for the stressed fish or diseased fish.

Sudden water temperature rise or drop

Water temperature is a crucial part of any aquarium. If your temperature is very low or hot, your fish may even die.

When the water temperature drops too low in the aquarium, they will lay still at the bottom of the tank to conserve energy.

If the water temperature increase high, fish will stay on the bottom cause that’s where oxygen levels will be higher.

The high temperature will also trigger your fish’s metabolism, and higher metabolism means higher food consumption and higher waste.


  • Use a heater with a digital controller to regularly check your aquarium temperature.
  • Try to maintain the optimal temperate for tank fish. Every species have different temperature requirements.
  • Do not keep coldwater fish with tropical fish in the same tank.

Unstable water parameters

Fishes are sensitive to unstable or imbalanced water parameters in their freshwater tank. There are some reasons why water parameters are not stable:

  • Overcrowing fish.
  • Broken filtration equiment.
  • Overfeeding.

Ammonia Poisoning

Every time you see a sudden change in any one of your fish. First, you should check whether your tank water parameters are normal or not. Ammonia poisoning is one of the deadly and standard conditions for almost every aquarist.

Ammonia Poisoning symptoms

Causes of Ammonia Poisoning

  • Overcrowding.
  • Overfeeding.
  • Adding fish in an uncycled tank.


  • Do a 25-50% water change to dilute the concentration of ammonia. Use dechlorinated water for your tank.
  • Do not overfeed your fish. An extra amount of food can affect your tank’s biological balance.
  • Cycle your tank if it’s a new setup.
  • Monitor ammonia levels weekly.

Diseases That can cause fish to lay at the bottom of the tank

Poor water quality or off-balance water chemistry can trigger a disease outbreak among fish. As mentioned above, you should have a small separate tank for diseased fish. This way, you can monitor the individual fish’s health.

White spot disease

The white spot disease is caused by a parasite named Ichthyophthirius multifiliis. 

Symptoms of white spot disease

  • Rub against the substrate and other rough surfaces inside the aquarium.
  • Lay at the bottom of the tank.
  • Lack of appetite
  • disorientated swimming.


  • A weekend immune system of the fish.
  • Poor diet.
  • Improper transfer from store to home tank.


  • Medicate the affected fish for 10-14 days in a separate tank, using formalin, malachite green, copper sulfate, or methylene blue.
  • You can also try giving fish a potassium permanganate bath.
  • In this case, you can seek a veterinary doctor’s help. If you can not treat your fish correctly, your fish might die.

Visible Wounds

Visible wounds are an invitation for disease. Try to separate them as soon as you see a wound fish. Quarantining wounded fish will help them from being bullied.


  • Fin nippers.
  • Bullied by other fish.
  • Fight for territory.
  • Bumping into decorations with sharp edges.


  • Identify the factors that contributed to the injuries occurring in the first place.
  • Separate fin nippers, bullies, or territorial fish.
  • Replace sharp-edged decor items with smoother ones.
  • Treat the wounds, and prevent infections using an antibacterial solution like MelaFix.

Bottom dwellers

Why Do Fish Lay At The Bottom Of The Tank
Image source: flickr.com

So, what is a bottom dweller fish?

A bottom-dweller fish means a fish that spends most of the time at the bottom of the tank. Fish Like shrimp, Cory catfish, and Kuhli loaches.

Bottom feeders

The bottom feeder prefers roaming at the bottom of the tank, and they will eat fish food as it sinks to the bottom or scavenge for the leftover among the substrate. Bottom Dwellers are also called bottom feeders.

Resting fish

Like every animal, fish also rests and sleeps, and they do these at the bottom of the tank. If your fish are healthy, they will rest between sessions of active sessions of swimming.

Provide enough hiding spots for your fish. Hiding spots will help your fish to be stress-free.

Older fish

As your fish age, they might tend to rest near the bottom of the tank. Tank or aquarium fish have a short lifespan, and the average lifespan of aquarium fish is around 3-5 years. The more they aged, the more they tended to rest.


When you introduce a fish to a new tank or aquarium, it will try to find a hiding spot as soon as possible within your tank. If your tank does not offer any hiding spots, they will probably lie at the bottom of the tank.


Always have a separate tank. This tank will help you to monitor the diseased fish closely. It would be best to treat your diseased fish separately from other fish.

Hey, I am Shuvradeb Biswas a content writer. Fishkeeping is my hobby. There are many problems I faced during my first fishkeeping. So, I made the KeepingWorld.com blog to help new fishkeepers.

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