Over the past few months I have gotten a ton of letters from readers wanting to know more about recognizing and diagnosing diseases in goldfish and koi. I am, of course, all in favor of hobbyists educating themselves on fish diseases.

But the truth is, delving into the subtleties of signs and symptoms, divining the likely disease-causing agent and sorting through the myriad of partially effective treatments is not a good use of your time — unless you have an unusual and intense interest in fish health as a hobby in its own right. Ornamental fish disease treatment is gambling with the odds stacked heavily against you.

Most hobbyists, I suspect, are interested in keeping their fish healthy and would rather forget about fish diseases. If this sounds like you, then your time would be better spent improving your tank and pond management skills. The single-most effective method for coping with fish health problems is to prevent them. And the single greatest cause of fish health problems is poor tank or pond conditions.

For example, the problem most frequently reported by goldfish keepers, such as Tina Vitelli of Massachusetts, is a goldfish that cannot stay upright — so-called swimbladder disease. In almost all instances this is caused by a simple digestive problem, one easily cured by changing the feeding regimen. Neither the swimbladder nor a disease-causing organism is involved. Yet hobbyists toss away incredible sums of money on fish drugs trying to cure this "disease" only to have the fish die from what is essentially a bellyache.

If you notice that one or more of your goldfish has trouble staying upright, that the problem is intermittent and that it occurs regularly, think "diet." The animal is getting too much of the wrong form of food. Flake foods and dry pellets are notorious for producing this balance problem in goldfish. It is an artifact of their weird shape and thus their internal organ configuration. (Notice that this problem is never observed in koi, which eat the same foods.)

In an aquarium the problem can be remedied by eliminating flakes, cutting back on pellets and presoaking them when used. Substitute parboiled shelled peas and other vegetables. If you are the culinary type, try making your own goldfish cakes (many books contain recipes).

Tina mentioned in her letter that she planned to build a garden pond. I guarantee that this will solve the problem. Why? Her goldfish will spend its time grazing on algae, plants and aquatic invertebrates. Supplementary feeding with pellets need only be a minor part of the diet. This is why balance problems are virtually non-existent in goldfish kept in properly managed ponds.

What is a properly managed pond? One in which the fish load is low enough that the animals could do nicely on pond plants and invertebrates if you went on vacation for a week or more. In a properly managed pond you should not have to feed the fish nearly as often as when they are kept in an aquarium.

Tanked Garage
Q. I have a 60-gallon aquarium in the garage that is doing nothing but collecting dust. The aquarium is complete, with rocks, filters, heater, lighting and so on, but I have no place in the house for it.

I was wondering if it would be okay to set it up in the garage. I would like to raise some orandas or similar goldfish. Would the fumes from the car be trouble? Would I need to keep the heater in the tank when the weather gets cold? And, would summer weather make the tank too hot?

A. There is absolutely no reason why you can't set up a fine goldfish tank in your garage, using a few precautions. First, make sure the tank sits on a sturdy, stable stand. There can be lots of activity in a garage and inevitably the tank and stand will sustain bumps and knocks.

Locate the tank in a low traffic area, if possible. The less activity around the tank, the better. You also want to avoid hanging tools or other items on the walls near the tank. There's nothing like a shovel falling off the wall and crashing through a 60-gallon tank to ruin your day.

Second, I would not store insecticides, herbicides or other house and yard chemicals anywhere near the tank. One little spill and your fish are dead. Keep volatile chemicals — gasoline, paint thinners, etc. — in a separate storage shed if you have one.

Third, install a lid on the tank. This will keep pollution-laden dust and other harmful substances from floating into the water. It may also prevent the neighborhood cat from dining on your fish.

If the garage stays above 40 degrees Fahrenheit there is no need to worry about a tank heater for orandas. Some varieties of fancy goldfish, however, fair much better in warmer winter waters — where temperatures rarely drop below 58 degrees Fahrenheit.

If your winter temperatures are consistently below this mark a tank heater may make sense. Most quality tank heaters can be adjusted to work at a lower range than standard tropical temperatures.

You can use any standard outside power filter. Be sure to maintain fresh activated carbon in the filter to remove errant gases and chemicals.

I doubt summer temperatures will get any warmer than in an outdoor pond exposed to bright sun. But, water circulation from a properly sized power filter should help keep the water cool. Remember, goldfish produce far more waste than tropicals, so it makes sense to get a power filter that is even a little too large for the tank. If the weather turns unusually hot, you can place a small portable fan facing across the top of the tank with the hood at least partially open. The air flow over the water surface will cool from evaporation.

I would also recommend a tank light that would be kept on for five or six hours a day. Natural daylight tubes will help bring out the colors of the fish. Otherwise, you will find that their colors will fade. Good lighting is especially important for maintaining the rich blacks of moors and related varieties.

Planned Pond
Q. I just received my first issue of AFI today and think it's great! I hope you have some plans for articles on ponds coming up. I plan on constructing two goldfish ponds and two koi ponds later this year. We live on the Oregon coast, so I hope not to have to move the fish indoors during winter. I am told that if I build my pond 6 to 8 feet deep the fish will survive all winter outdoors. Any comments?

A. Over-wintering koi and goldfish outdoors is easy if there is little chance of surface ice forming for more than a few days. Just maintain the pond as usual, keep the filter running and do not feed until water temperatures stabilize above 55 degrees Fahrenheit.

Assuming you do get extensive surface ice, the secret to over-wintering goldfish and koi outdoors is to 1) have plenty of free water per fish available under the ice and 2) keep an opening in the ice to allow some gas exchange.

Depth is certainly the key to maintaining free water below the ice. A depth of 6 to 8 feet is good for your area. The entire pond need not be that deep — two-thirds might suffice — but, more is always better.

I know many readers have not had problems, but one bad cold snap every few years or so and there go all your fish! Considering that goldfish and koi in outdoor ponds should live 20 years or so, winter extremes are worth worrying about.

For example, I have over-wintered pool comets in ponds about 2 feet deep for about eight years. All have made it through without problems, until last year. Ice came a week or two early and left a week or two late. All the fish died. The same thing happened in hundreds of ponds across the state. Everyone lost prize goldfish. Koi are even more sensitive to the vagaries of winter than goldfish.

A light fish load, which is about one goldfish per 10 square feet of pond surface area, or one 12-inch koi per 50 square feet of surface area, is equally important. And this assumes no winter feeding.

Given these guidelines, you can determine the minimum size of your pond based on the number of fish you would like to have. Suppose, for example, you want to raise eight koi. The pond should have a surface area of at least 400 square feet and be 6 feet deep. This amounts to 2400 cubic feet of water or 18,000 gallons.

For those in the pond community who are about to overreact, keep in mind that these guidelines are for "limited-risk" management. You can certainly try a smaller pond, or more fish, but you increase risks and problems.

Use one or more floating, thermostatically controlled de-icers to keep some surface area ice free. Gas exchange is crucial for successful over-wintering. Leaves and debris on the pond floor will not matter if gases can move in and out of the water column.