Angelfish Sitting At The Bottom Of The Tank: Reasons & Solutions

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As an aquarist, pretty frequently, I notice changes in my angelfish’s activity. For example, there were times when I saw my angelfish sitting at the bottom of the tank. As I studied the issue, I found a few fundamental causes that impact my fish’s health. To make sure you take the right approach, I decided to share what I’ve learned.

Angelfish typically sit at the bottom of the tank due to an underlying ailment, such as Dropsy, Velvet, Ich, and swim bladder disease. However, angelfish may also lie at the bottom due to stressful conditions, such as inappropriate ammonia, pH, and temperature levels.

As we move forward, I will share a few other reasons that may force your angelfish to dwell in the bottom section. I will also take you step-by-step on what you should do to treat your angelfish and prevent its state from deteriorating.

Why Is My Angelfish Lying on the Bottom of the Tank?

Angelfish are not bottom dwellers. As such, it isn’t necessarily natural for them to sit at the bottom of the tank. If your angelfish are spending a lot of time at the bottom, one of the following is to blame:

1. Old Age

Like people, fish tend to become less active as they age. Angelfish can live an average of ten years, and they may slow down as they approach their final moments.[1] That is because they don’t have the energy to swim as they once did; some of them might choose to rest by sitting at the bottom.

However, sitting at the bottom isn’t the only phenomenon you’ll notice if your angelfish has aged. You may also notice weight loss, bulging eyes, and discolored skin. Those are typical signs for a relatively old fish.[2]

2. Stress

Stress is one of the most common causes of lethargy and timidity in fish. While angelfish have an aggressive streak, that doesn’t make them immune to stress. If your fish is too stressed, it may choose to dwell in the bottom sections.

Common causes of stress in angelfish, and fish in general, include:[3]

  • A sudden transition to a new tank without proper acclimatization
  • The presence of human traffic in the vicinity, not to mention the tendency the owner might have to knock on the glass.
  • Loud noises such as television sets
  • Harsh lighting, particularly the kind that doesn’t permit the angelfish to sleep, prevents them from enjoying a typical day/night cycle.
  • Poor tank conditions such as overcrowding and the presence of aggressive fish.

Also Read: Stress In Angelfish

3. Low Water Quality

Angelfish require a cycled tank with specific parameters. Insufficient quality water is harmful to fish. It can lead to adverse consequences such as loss of appetite, discoloration, and the sort of lethargy that forces the fish to lie at the bottom of the tank. 

Some problematic factors in the water that can adversely affect the behavior of an angelfish include:

  • Water pH – The wrong pH will cause considerable discomfort in your angelfish, making them more susceptible to illnesses. The wrong pH can also kill them. Angelfish typically require a pH ranging from 6.5 to 7.1.[4]
  • Temperature – An angel’s tank shouldn’t be excessively hot or cold. High temperatures will strip the water of its oxygen, forcing the fish to lie at the bottom where the water is colder and more oxygen-rich. On the other hand, low temperatures can cause sluggishness, which also compels your angels to frequent the bottom.
  • Toxins – The ammonia, nitrates, and nitrites in your tank can poison your fish. These toxins are associated with symptoms such as listlessness, weakness, discoloration, loss of appetite, and gasping. The presence of toxins may drive an angelfish to the surface for a time, but their physical weakness will eventually pull them to the bottom.
  • Lack of Oxygen – The temperature is not the only factor affecting oxygen levels in a tank. You can create an oxygen deficiency by crowding your tank, allowing toxins to grow in concentration, and failing to install suitable filters and pumps. Angelfish cannot survive without oxygen. After gasping at the surface for a while, they will fall to the bottom.
  • Overcrowding – Fish are explorers; they want as much room to swim as you can offer them. Angelfish have nothing to do in a crowded tank because they don’t have the room to maneuver. That could quickly force them to remain at the bottom.

4. Disease

Some diseases, such as dropsy and velvet, are so severe that they sap an angel’s strength. Once it is too weak to swim, it naturally descends to the bottom. Others have a more direct impact on the angel’s swimming behavior, for instance:

  • Swim Bladder Disease – The swim bladder affects an angel’s buoyancy. For that reason, when the organ is injured or stricken with diseases, the fish’s ability to swim suffers. When they contract swim bladder disease, some fish will swim erratically. Others will entirely lose their ability to swim, which will force them to stay in place at the bottom.
  • Ich – Ich is an illness that covers your angelfish in spots. It also causes itching. Some fish will rub themselves against the substrate as a consequence of Ich. Others will choose to sit at the bottom.[5]

How to Treat Angelfish that are Lying at the Bottom?

As you have noticed, angelfish that frequent the lower sections of the tank could mean that the fish is suffering for several reasons. If you wish your fish to stop sitting at the bottom, I suggest taking the following steps:

1. Improving Water Conditions

It isn’t enough to cycle the tank before you introduce your angels. You should also maintain the right parameters. That includes a pH of 6.8-7.8, temperatures of 78-84 degrees F, and a hardness of 3-8dKH.[6]

To measure those, I highly recommend getting the API Aquarium Test Kit (link to Amazon). That fantastic bundle will measure your pH, ammonia, nitrites, and nitrates within minutes and lasts forever. That is the particular kit that I use with great success.

If you’ve measured a pH lower than 6.8, or ammonia levels that are too high, please perform more frequent water changes. That typically happens when rotten plants and debris accumulate within the tank, releasing nitrates and other toxins. I suggest replacing 15-25% of the water weekly.

To prevent toxins from spiking in the future, you need a decent filter that will remove contaminants. It would help if you also vacuumed the substrate and removed any dead plants and animals, food, and leftovers you see in the water.

I recommend installing a high-quality heater to prevent drastic temperature shifts that can directly stress your angelfish. I personally use the Cobalt Aquatics Neo-Therm Pro Aquarium Heater (link to Amazon) and am entirely satisfied with it. I also reviewed it here.

If, besides lying at the bottom, your angelfish is also opening and closing its mouth rapidly, your tank probably lacks oxygen. Luckily, treating that is relatively easy. All you have to do is to put in a few air stones that will oxidize the water. I use the Pawfly 1 Inch Air Stone (link to Amazon).

2. Eliminating Stress

If your angelfish are stressed, start by putting the aquarium in a quiet room away from areas that receive a lot of foot traffic. It would help if you also avoided places with loud electronic devices such as air conditioners, television sets, radios, and the like. 

I also recommend keeping the tank away from windows that expose it to direct sunlight to avoid overheating. It would also be best if you prioritized a filter that operates quietly. Angelfish are quite gentle and require relatively gentle currents.

Also, when you add new fish to the tank, please create some acclimatization. It would be best if you didn’t stress your angelfish by pouring the new tankmates as they are. Instead, you may put the new fish in a plastic bag while letting it float over the surface for a while. 

If you notice that the angelfish’s companions are bullying, try to rearrange the tank’s decorations. That will eliminate pre-existing territories and force all the fish in the tank to seek new ones. That also includes angelfish that attack other fish.

I would also recommend pairing your angelfish with suitable tankmates such as Corydoras catfish, mollies, and platies.[7] If you have aggressive fish such as bettas or gouramis, you can either remove them or add a divider to protect the angels from assaults.

When it comes to lighting, I suggest using programmable lights that will switch off after twelve hours to give angelfish the darkness they require to rest. Try not to leave the lights on all night; that will distract your fish’s inner clock.

Bear in mind that an angelfish tank should have plenty of foliage, not to mention decorations. These will create hiding places that stressed angelfish could use to stay out of sight. However, make sure not to overstuff your tank. Try to maintain that delicate balance.

Regarding the tank’s size, take into account that angelfish require a tank of at least 20 gallons. Large groups of angelfish require even larger aquariums. Anything smaller will confine them, creating uncomfortable conditions that will stress the angels.

Also Read: Why Do Angelfish Hide?

3. Treating Diseases

Angels sitting at the bottom of the tank because of diseases will most likely manifest additional symptoms, depending on the disease. You should treat each angel according to the illness you have identified. 

An angelfish that frequent the bottom due to a swim bladder disease will most likely present buoyancy symptoms. For instance, it may sometimes float upside down and struggle to maintain a balanced position. 

You can treat swim bladder disease by giving your angels fiber-rich foods such as daphnia. Another approach would be to stop feeding your angelfish for three days. Do that while raising the temperature to 78-80 degrees F. Then, feed your angelfish some peeled peas.[8]

As was mentioned, a fish with the Ich will probably develop white spots resembling a sprinkle of salt grains.[9] You can treat Ich by raising the temperature, improving the water conditions, using aquarium salt, and deploying medicine that combats parasites prescribed by a professional.[10]

Dropsy, in the earlier stages, will respond to Epsom salt and antibacterial medicine. With velvet, you can experiment with formalin, copper sulfate, and methylene blue.[11] However, if you suspect that your angelfish is sick, I highly recommend consulting a vet rather than trying to treat it on your own.

Do Angelfish Sleep on the Bottom?

Yes, angelfish sleep on the bottom. At night, they will descend to the substrate, their colors will fade, and they will stop moving. They are more likely to fall asleep when the lights are switched off.

Some people confuse dead fish with sleeping fish. However, it should be noted that sleeping angelfish are not entirely still. If you observe them closely, you will notice that their fins are still moving. But they are slow and sluggish.

The easiest way to determine whether a fish is sick, dead, or merely sleeping, is by introducing new stimuli. Switch the lights on and either find a way to prod the angelfish or add some food. A healthy fish will react to the food by swimming up. A sick fish is more likely to stay at the bottom. A dead fish won’t move.

Also Read: Angelfish Laying On Its Side


Angelfish may sit at the bottom of the tank for numerous reasons, ranging from advanced age to underlying ailments. Since sometimes, it is challenging to determine the precise reason, the best approach would be to treat all possible causes.

To do that, I recommend starting with the water parameters. Measure the pH, nitrates, temperature, and ammonia, and make sure that they suit your angelfish. However, even if the parameters are out of range, avoid making abrupt changes. That could stress your angel even more. Make gradual adjustments. 

If you suspect that your angelfish is suffering from a swim bladder disease or Ich, the best approach would be to consult a vet. They will be able to prescribe the right medication. Either way, I suggest moving your sick angel to a different tank to avoid further contagions.