A Staff Report from the Straight Dope Science Advisory Board

If a goldfish is swimming on its side, is this a bad sign?

October 6, 1999

Dear Straight Dope:

My father-in-law recently won three goldfish as a table prize at a party. When he brought them home, two of them were intermittently swimming on their side. While I know nothing about specific signs of dying fish (or goldfish), this did not seem to be a good sign. Sure enough, within a few hours one goldfish had bit the dust and by the next morning, goldfish #2 swam no more. I realize that goldfish are not known for a long lifespan, but I'm still curious to know:

1) Is this behavior (swimming on the side, and even upside down) specific to goldfish, or do other fish exhibit this same behavior?

2) Why does the fish do this? Is it a more relaxing position? Is some internal balancing mechanism in the fish not functioning? Thanks.

Several fish diseases can cause fish to swim like drunks (and some species of fish swim upside down normally!), but the most common one affecting goldfish is swim bladder disease. Your fancy globoid-shaped goldfish - orandas, ranchus, ryukins, fantails and moors - are especially susceptible to this condition. Sometimes they recover and sometimes they don't. I had a goldfish that would float belly up for awhile after every meal, and then seemed normal the rest of the time. Bad indigestion, I'd say. "Had," I say, as I've gone through quite a number of goldfish, myself. The pet store I patronize gives you a "fish card," and when you get ten stamped on the card, you get $5 worth of free fish. "Hey, this is a good deal for somebody like me!" I told them cheerfully. They look at me like I'm a murderer every time I turn in my completed card to collect my free fish.

The swim bladder controls bouyancy in fish. It's a small sac in the front of the abdomen which fills with air to increase bouyancy and deflates if the fish needs less. Goldfish have a pneumocystic duct which allows air to leave the swim bladder through the digestive tract, so if there's impaction of food--one possible cause of swim bladder problems--this messes things up.

A number of things can cause swim bladder disease, and goldfish do seem to be predisposed to it. The egg-shaped fishes described above might get it more often because they have been bred into such strange shapes that their guts are squeezed into a small part of the abdomen. It can also possibly be caused by a virus or bacterium, but usually does seem related to diet. One of my books recommends soaking the dry food before feeding, or changing to live or frozen food to lessen the chance of food impaction. It's also a good idea to just stop feeding them for a few days if you notice them behaving oddly after eating, and sometimes that will take care of the problem.

Goldfish are dirty fish, and it's important to do partial water changes frequently to keep them healthy. A friend of mine keeps a second fishbowl full of water around, then simply dumps the fish in the clean one (which has been sitting around, so is chlorine-free and at room temperature) while he washes out the old one. Serious goldfish husbanders of course frown on keeping fish in bowls, but this guy's fish has lived longer than mine ever do (and I do everything right), so I try to keep my mouth shut about it.

The cure-all for most goldfish diseases that's always worth a try is adding 1 teaspoon of uniodized table salt per gallon to the tank. ("Why should I listen to this woman who sucks at fish rearing?" I hear you ask. Don't get snotty, I'm just telling you what the experts say here.) Potentially goldfish can live seven or more years in an indoor tank and tend to live longer (up to 20 years) if they're subjected to colder water for part of the year, such as in an outdoor pond.

There are more drastic measures one can take to remedy swim bladder disease in fish, and before you laugh, realize that some of these ornamental goldfish--especially in Asia--can be very pricey. Some veterinarians will aspirate a defective swim bladder in a fish with a needle, releasing some of the air. That's not all. Some people take their sick fish in for surgery to remove part of the swim bladder, called a partial pneumocystectomy. There are also vets who put fish under general anesthesia, do X-rays on them, and even give them chemotherapy for cancer (no need for a wig, at least). I would think that unless your father develops a strong sentimental attachment to the last little guy, assuming he has not yet passed on, such procedures would not be cost effective for a fish he won as a table prize.

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