Goldfish and Aquarium Board Articles
Buoyancy Issues in Fancy Goldfish
(aka flipover, Swim Bladder Disease)

By Betty

Fancy goldfish are predisposed because of their body shape to develop problems controlling their position in the water. This is manifested in several ways. Often goldfish flip upside down, can't right themselves, and may be stuck at the top of the tank upside down. Some may do head or tail stands while others may be stuck on the bottom of the tank. This is often called Swim Bladder Disease or flipover, however I prefer to call it buoyancy problems--the fish isn't able to control his or her position in the water. Why call it buoyancy problems? Because there is more than one cause and sometimes it's not the swim bladder messing up, but gas in the gastrointestinal tract that causes the flipping. Buoyancy problems may be transient (food-related gas, or inflammation from an infection) or permanent (malformed swim bladder, compression of the swim bladder, or damage to the mechanisms for controlling gas pressure in the swim bladder) or can be from tumors or cysts in the abdominal cavity. While there is all sorts of advice online about how to treat buoyancy problems, there is little systematic research on what does and doesn't work or even on the physiology of why buoyancy problems happen. This article will attempt to cover the anatomy and physiology related to buoyancy issues and recommend a course of action if your goldfish is having trouble controlling his or her buoyancy.

Things that affect buoyancy

The swim bladder is a two lobed balloon-like organ positioned at the top of the abdominal cavity. Its function is to allow the fish to control their buoyancy or position in the water. Doc Johnson has some pictures up of the internal anatomy of goldfish and there are pictures of my black moor Lumpy's undersized swim bladder in our Goldfish Internal Anatomy Article. We are also compiling pictures of swim bladders from necropsies (graphic) and various cases with x-rays.

According to Dr Richard Strange's FIsh Physiology Course CD, there are two mechanisms for controlling buoyancy :

  1. Vascular mechanisms: There are three vascular areas for gas exchange between the swim bladder and the bloodstream. The rete mirabile, the gas gland and a resorptive area in the tissue of the pneumatic duct. Strange says the rete mirabile and the gas gland work together to increase pressure in the swim bladder. The rete mirabile maintains a pressure differential between the blood and gas bladder and keeps it from losing gasses. The gas gland cells release carbon dioxide and lactic acid causing hemoglobin to release oxygen which results in an increase in partial pressure allowing oxygen and nitrogen gasses to flow into the swim bladder.
  2. The pneumatic duct is a tube that runs between the esophagus and the swim bladder. Goldfish may gulp and burp air to alter the pressure in the swim bladder. It is unclear to what degree they actually use burping and gulping to decrease or increase the pressure in the swim bladder. Doc Johnson says it's used only for expelling air.

Based on this, anything that adversely affects the small capillaries of the rete mirabile, the gas gland, the resorptive area or the pneumatic duct could affect the goldfish's ability to increase or decrease the inflation of the swim bladder. Inflammation caused by bacteria or viruses is one likely cause. High nitrAte levels could also affect these blood vessels because nitrAte (converted to nitrIte in the blood stream) may cause vasodilatation. Identifying and treating/removing the cause of the inflammation are essential to preventing permanent damage.

However inability to control buoyancy (especially being stuck on the bottom), may simply be caused by compression of the swim bladder as the goldfish grows because the rounded body shape does not allow enough room for the swim bladder to grow to the size needed to maintain buoyancy. If the swim bladder is malformed or compressed by the body, there is not much that can be done to inflate it. The only successful treatment so far was developed by Dr. Greg Lewbart and involved inserting a tag into the muscle by the dorsal fin and attaching a cork to it to keep the fish upright. Tumors and other internal conditions such as cysts can also affect buoyancy. You can read about a large renal cyst in an oranda here. In this case, the cyst was compressing the swim bladder and keeping it from being able to inflate to control buoyancy.

Another thing that may cause buoyancy issues is gas in the GI tract. I think there are two ways that goldfish can get gas in their GI tract:

  1. from swallowing air - if they gulp air and their esophageal sphincter (the muscle between the esophagus and the stomach) isn't strong enough to keep the air from getting into their digestive tract.
  2. from gas producing grains found in many commercial goldfish foods. Gas is formed by bacteria in the colon from fermenting certain starch or sugars. Several foods that may contribute to gas are in fish foods (wheat, soy, and legume seeds). Digestion of these starches by animals requires an enzyme produced by bacteria present in the GI tract. These bacteria produce hydrogen, methane and carbon dioxide gases (1, 2, 3). This may occur after the use of antibiotics because antibiotics disrupt the normal flora of the GI tract, thus opening up a niche for the gas producing bacteria to over-colonize.


If a goldfish is flipping, the first thing to do is check your water parameters. Some people think high nitrate can cause flipping. As mentioned above, it is possible that high nitrAtes affect the vascular mechanisms for controlling the amount of air in the swim bladder. If your nitrAte is running above 40ppm, do partial water changes to lower it. Fast growing plants may also help as would vacuuming your gravel thoroughly (the bacteria that eat debris in the tank also produce ammonia which gets converted to more nitrAte). If you can't keep nitrAte at tolerable levels, consider setting up a larger tank because the extra water will help dilute nitrAtes.

The second step is to rule out bacterial or parasitic infections. Things to look for:

and treat appropriately.

The third thing to do, would be to rule out gas in the gastrointestinal (GI) tract. If the goldfish flips after eating or you see farting or floating poop, that's an indication that there may be gas in the GI tract. So what do you do about that?

Another common recommendation is to fast the goldfish (to rest the GI tract) and then feed only green peas which have a laxative effect. I prefer the big meal of fresh foods approach because that way you can quickly rule out if it's the commercial food causing gas and start antibiotics if it's not a food allergy causing the flipping.

Changes in buoyancy may be a symptom of an internal bacterial infection as the inflammation could be affecting the vascular mechanisms for controlling air pressure in the swim bladder. This is especially likely if the fish quickly goes from a floater to a sinker. Consider feeding antibiotic food ASAP. To kill two birds with one stone, you could make up a homemade gel food with Acidophilus to reduce gas in the GI tract and add Kanaplex (kanamycin sulfate) to the gel food to treat the internal bacterial infection.

Some goldfish gulp air at the surface and air gets into their GI tract. Signs of this are floating after gulping air, poop with air bubbles in it and/or farting. For goldfish who gulp air and then get floaty, the first thing to do is make sure your water has plenty of dissolved oxygen, then rule out problems that could reduce gas transfer at the gills such as bacterial or parasitic gill diseases or poor water quality (e.g. high nitrItes can cause a fish to suffocate even if sufficient oxygen is available in the water). Once you've treated the problem causing the goldfish to gulp air (if gulping air into the GI tract was the problem), the buoyancy issues should resolve.

Flipping is stressful for the goldfish and chronic stress is a bad thing because it causes the release of epinephrine and corticosteroids, which reduce the effectiveness of the immune system, make it more difficult to regulate osmotic pressure, cause high blood sugar and other changes in physiological function that will likely result in susceptibility to disease and early death. Early diagnosis and treatment are essential to addressing factors like bacterial infections or food allergies that can be treated to minimize permanent damage.

If you have ruled out water quality, bacterial infections, gulping air and food allergies, there are harnesses you can make to keep your goldfish upright, however these may cause sores and may not be a long term solution.

For a goldfish that is flipped and at the top of the tank, there has been some success with surgically inserting a stone into the abdomen to weight down the bottom of the fish and help it stay upright. Doc Johnson documented a surgery where he implanted a quartz stone into a black butterfly telescope goldfish named Hoover to keep him upright. Currently Robyn's fancy goldfish Randi is being treated with Acetazolamide, a carbonic anhydrase inhibitor that should slow down the gas gland cells production of gas in the swim bladder. Janet's Gock had surgery to remove part of his swimbladder.

For a goldfish that is stuck at the bottom of the tank, Dr. Greg Lewbart has developed a prosthesis where he inserts a tag into the muscle by the dorsal fin and attaches a cork to it to keep the fish upright. Early results appear to be promising. A harness/sling worked just fine for my moor Bugsy, for the last year of his life.

Consider locating an aquatic vet for diagnostic testing and treatment assistance.

In Summary

Buoyancy issues may have several different causes, some of which we can treat. Quickly identifying and treating the causes we can do something about is essential. If the underlying causes can't be resolved, long term outcomes are not good for goldfish who have buoyancy issues. If the buoyancy problems don't resolve, harnesses may provide some relief. Surgical options may also provide some relief and allow the goldfish to swim somewhat normally, however, they would still most likely result in stress which would ultimately result in susceptibility to illness and early death. The toughest decision comes when you've done everything you can and the goldfish is still not able to swim normally. At what point is the quality of life so poor as to consider euthanasia? Not an easy question.


So what can we do to help prevent buoyancy problems in fancy goldfish? It's not possible to prevent congenital malformations or to prevent compression of the swim bladder. Both of these problems may show no symptoms in young goldfish, but will manifest as the goldfish grows. It's also not possible to reverse damage to the mechanisms that control pressure in the swim bladder. We can however prevent buoyancy problems that arise from infection, inflammation or from food allergies by keeping our goldfish healthy by:


I would like to thank the people who contributed ideas and feedback for this article including Liv, CaptK, eBay Queen, and Tamianth. The original thread can be found here.

Further reading:

goldfish flipover, flipping, treatment, flip over, swim bladder, swimbladder, upside down, floating, sinking, headstanding, tailstanding, head standing, tail standing.

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