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Why is my fish resting at the bottom and can't open its mouth?

Updated on September 23rd, 2025

Pet's info: Fish | Unknown - Fish

My fish can’t open it’s mouth, and Is resting on the bottom of the tank, has a swim then goes back to the bottom of the tank

3 Answers

Most Helpful Answer

Angel Alvarado, LVT

Answered By Angel Alvarado, LVT

Licensed Veterinary Technician

Published on December 5th, 2017

Check the water chemistry and quality first. Elevated ammonia or nitrite levels can be toxic. Partial water changes can be done to stabilize and improve water chemistry. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. For goldfish, a range of 65F to 72F
is recommended.
Check the filter and rinse the sponge with tank water, not tap water, to spare beneficial bacterial populations and to maintain water quality. The tank may not be large enough to support 5 goldfish. Generally, 20 gallons should be allowed for the first goldfish then a 10 additional gallons should be provided for each additional goldfish. This is due to the larger than average bio load (wastes) they produce. Consider a larger tank or decrease the number of fish in one tank. Use a filter that is rated for at least twice the volume of the tank and add an airstone and pump for increased oxygenation.
Plain aquarium salt (NOT table salt). Can be used as a general tonic. It will reduce stress, improve gill function, aid in any recovery and may treat or prevent minor infection. Dissolve 1 teaspoon of salt per gallon of water in a cup of tank water and gently pour it into the tank. Treat for 10-14 days. When performing water changes, add salt only to the amount of water being replaced, not the entire tank volume.
Vote Icon4Pet Parents found this answer helpful

Related Answers from Veterinarians

  • Answered By Angel Alvarado, LVT

    Licensed Veterinary Technician

    Published on September 4th, 2018

    Ideally, one goldfish should have 20 gallons of water. The reason being that goldfish produce a larger than average bio-load (wastes) than other fish. One fish can quickly overwhelm a small tank and filter.
    If you have a smaller tank, use a home test kit to monitor ammonia, nitrites and nitrates. When ammonia or nitrites begin to rise, it is time to perform a partial water change.

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    1Pet Parents found this answer helpful

  • Answered By Angel Alvarado, LVT

    Licensed Veterinary Technician

    Published on April 29th, 2019

    Check the water quality again use a liquid home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee
    Aim for an absence (0 ppm) of ammonia AND nitrites. Nitrates can be 20 ppm or less. Perform another partial water change, no more than 30% total volume, at a time. Use only conditioned water that is temperature matched to prevent stress or shock. Goldfish are cold water fish and do best between 65 F and 72 F.
    Additionally, a 10 gallon tank may be insufficient for 2 goldfish and a Black Moor. Goldfish produce a larger than average bio-load (waste) which can quickly overwhelm a small tank and after. Ideally, provide 20 gallons for one goldfish and an extra 10 gallons per fish. The filter should be rated for at least twice the volume of the tank. Even with a string filter, partial water changes and regular cleaning/vacuuming will be needed to maintain water quality.

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    2Pet Parents found this answer helpful

Smart Picks for Smart Questions

Vet Q & A
My goldfish's mouth is stuck open. What's wrong and how can I help?
eIf you can, look in the mouth for foreign bodies (gravel, food, etc), tumor or any redness, swelling or discharge. You should also check water chemistry. If ammonia or nitrites are elevated, perform daily partial water changes to stabilize chemistry and maintain water quality. Use only aged or conditioned water that is temperature matched to prevent further stress or shock. Goldfish do best in cooler waters, between 65F and 72F. Trauma is also a possibility. A fractured or dislocated jaw can be the result of hitting the glass or tank furniture or from bullying. Swelling from infection is also a possibility. Monitor for redness, bruising, lethargy or loss of appetite. A broad spectrum antibiotic can be used if necessary. Find one, such as maracyn or kanaplex, in the aquarium section of the local pet or fish store. Follow label directions carefully and remove the carbon filter insert during treatment if indicated. Maintaining adequate water quality and parameters will aid in any healing. Plain aquarium salt (NOT table salt) can be used as a general tonic. It will reduce stress, improve gill function, aid in recovery and may help treat minor infection. Dissolve 1 teaspoon per gallon of water in a cup of tank water and gently pour it into the tank. Treat for 10-14 days. When performing water changes, treat only the amount of water being replaced with salt, not the entire tank volume.
Updated on September 23rd, 2025
Health & Wellness
Why is my goldfish not moving and staying at the bottom of the tank?
Since the others in the tank are behaving normally, this one may be sick or injured. Ideally, it should be separated into a quarantine or hospital tank Check water chemistry first, even if you've done it already. You can use a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0ppm) of ammonia and nitrites, with nitrates at 20ppm or less. Perform partial water changes to correct or stabilize water chemistry. Use only conditioned water that is temperature matched to prevent additional stress or shock. Goldfish are cold water fish and do best between 68F and 74F. Change no more than 30% of the volume at one time. In the absence of other symptoms or injury, medications cannot be recommended. You can use plain aquarium salt (NOT table or Kosher salt) as a general tonic to decrease stress, increase gill function and aid in recovery. Dissolve 1 tablespoon of salt per 2 gallons of water in a cup of tank water and gently pour it into the tank. Treat for 10-14 days then perform partial water changes to decrease salinity.
Updated on September 23rd, 2025
Health & Wellness
Why is my fish sick, not eating, gasping, and darting in its tank?
Check water chemistry first. Use a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence ( 0 ppm) of ammonia and nitrites with nitrates at 20 ppm or less. Perform partial water changes, no more than 30% at a time, to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Check water temp as well. Any of these can drive a fish to the surface. The "flashing" (darting about) can be due to infection (bacterial, fungal or parasites). Consider a broad spectrum antibiotic or an "all in one" product to treat multiple infections. Look in the Aquarium section of the local Petco for options. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.
Updated on September 23rd, 2025
Vet Q & A
Why is my fish struggling to swim, jumping, or lying at the bottom?
Check the water quality and temperature. Warm water will not hold as much oxygen as cool water and goldfish are cold water fish. Ideal water temp is about 21 C. Use a home water test kit to check parameters. Ammonia and nitrites should read 0ppm (parts per million) and nitrates can be 40ppm or less. If you don't have a test kit, most pet stores or aquarists will test a sample for free or for a nominal fee. Ensure adequate filtration and oxygenation. Use a filter that will comfortably handle twice the volume of your tank. An airstone will increase oxygenation. A tank hood or cover is recommended to prevent fish from jumping out.
Updated on September 23rd, 2025
Vet Q & A
Why is my betta struggling to swim with a curved spine and gasping?
Recheck water chemistry to confirm 0 ppm ammonia and nitrites with nitrates at 20 ppm or less. A pH of 7 is fine and they can adjust to more acidic water as long as the change is gradual. Temperature should range between 78 F and 80 F. Plain aquarium salt (NOT table salt or epsom salt) can be used as a general tonic to reduce stress, improve gill function, treat minor infection and aid in recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup or two of tank water and gently pour it into the tank. Perform partial water changes every couple of days to maintain water quality. Treat only the volume of water being replaced. Treat with aquarium salt for no more than 14 days then reassess the condition. An antibiotic, such as kanamycin or erythromycin, can be found in the aquarium section of the local Petco if the salt treatment doesn't help. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.
Updated on September 23rd, 2025
Health & Wellness
Why is my goldfish's mouth stuck shut? He won't eat or move.
Thanks for reaching out about Tennessee and including photos. If he can not open his mouth, he needs to see a veterinarian, the sooner the better. Concerns are an oral obstruction, fractured mandible or other problems. Check and correct water quality as pristine water parameters will be needed after a veterinary visit. Good luck.
Updated on September 23rd, 2025
Health & Wellness
Why is my goldfish swimming at the top, gasping for air, and stressed?
Thanks for reaching out about Kirky and including a photo, although the photo is out of focus. Swimming to the surface and gulping air is typically and indication of gill disease. Gill disease can be caused by poor water quality, bacterial infections, gill parasites, and metabolic disorders. First, check water quality for pH, ammonia, nitrites and nitrates. Correct problems. Make sure to treat tap water for several hours prior to adding to the tank. If water quality is correct, a veterinary visit for assistance in a diagnostic/treatment plan. A gill clip can be examined under the microscope to determine parasitic or other gill disease. Antibiotics added to the water typically cause more problems than benefit, altering biological filtration. Good luck.
Updated on September 23rd, 2025

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