Q. Every spring I look at my pond fish and hope the ones that look fatter than normal will lay eggs. My real hope is that the ones that produce babies will be the koi, the beautiful fantails, or even the long-tailed comets. But every year, with hundreds of tiny offspring, the babies are always short-tailed common comets. I've looked everywhere and cannot find information on the mating of goldfish and their offspring. I would love to learn how to tell the males from the females, which to mate with which, and all the other details of controlled spawning.

A. Goldfish and koi are the products of selective breeding. The many varieties that grace our tanks and ponds are the result of genetic manipulation. Thus, the controlled breeding you are interested in is natural and appropriate for this particular type of fish.

I could not possibly do justice to the topic here, so let me provide the basics and suggest you check out KOI USA and The Goldfish Report, two very valuable sources of information. The Goldfish Society, which publishes The Goldfish Report, also has an excellent handbook that covers goldfish breeding (Goldfish Society of America, P.O. Box 851282, Richardson, TX 75085-1282).

The traits we like in fancy goldfish and colorful koi come about by genetic manipulation through selective breeding. Breeders choose particular characteristics they like, such as long flowing tails, and then select males and females that strongly exhibit those characteristics, and mate them.

Unfortunately, most of the traits we find very attractive are recessive rather than dominant. That is, they do not express themselves well, or often, among the offspring. Thus, even if two long-tailed comets successfully mate, only a fraction of their spawn will have long tails. Most will have characteristically short tails — a dominant trait. Controlled breeding of successive generations with particular traits can often increase the proportion of babies showing the characteristic, but it may take 10 or 20 years to fix a trait well. Patience and a good eye for fish are musts. This is why "breeder" fish are so expensive.

Another factor weighing against fancy goldfish and brightly colored koi is natural selection. Fish with long flowing tails, bizarre body shapes and bright colors are just not competitive with their more natural brethren. They cannot get to the food as fast, so they tend to be smaller and underfed. Moreover, if anyone is going to be eaten by other pond critters or by larger fry, it is going to be the most unique specimens — those that stand out and are not fast enough to save themselves. Therefore, breeders cull fancy fry very early and segregate them in special breeding ponds where their competitive disadvantages can be minimized.

So, your lack of success in breeding a fancy variety is not too surprising. Left to her own devices, Mother Nature will try to produce normal, natural, ancestral variants of goldfish and koi, not the fancy ones you desire. If you want to experiment with selective breeding then you should find a male and female with the identical characteristics you want in the offspring. These animals should be kept separately from your other fish during breeding season. You can improve the spawn further by hand spawning and carefully culling out all the fry that do not have characteristics you bred for.

In my previous series on goldfish in AFI (October, November and December 1993 issues) I suggested some ways for distinguishing male and female goldfish. However, the most reliable way is to see who chases whom at breeding time. The chasee is the female, the chasers are males. Of course, even this is not 100 percent guaranteed because same-sex breeding behavior is often observed among fish.

Here, Kitty Kitty?
Q. I read AFI from cover to cover. I totally agree with you that a pond is much more than an outdoor aquarium in the ground. It is also dynamic and ever changing. With a pond comes nature, and though I don't care for the Colorado River toads that spawn in my pond, the birds, rabbits and even snakes (yes, rattlesnakes too!) are interesting to watch. I've seen coyotes, ringtail cats, dogs, and even javelina (wild boar) tracks.

But recently, I struck gold. Both magnificent and more than a little unnerving was the first time I opened the back door and came face to face with "Kitty" — our resident mountain lion. "Kitty" is welcome to come drink while I watch (from a distance). Ponds have much to offer beyond traditional aquariums — all you need to do is sit and wait. By the way, no raccoons.

A. Your experience illustrates quite nicely the magnetic attraction of water to wildlife. The sound of splashing water, in particular, can draw animals from very far away. A pond with a crashing waterfall or a babbling brook will have a greater diversity of wildlife visitors compared to a tranquil pool that is contemplatively quiet.

As you have discovered, pondkeeping can be a much more rewarding experience when you let the serendipity of nature have a free hand. I can imagine, however, that having seen your letter, some of our readers are dashing out to their yards to pave over their ponds.

Given "Kitty's" presence, I do not find it hard to understand why raccoons are scarce. I never considered mountain lions as a method for controlling raccoons, but I have not doubt that it works. Thanks for writing. You made my day.

But Do I Need One?
Q. My pond is approximately 1500 gallons — 15 feet long, 12 feet wide, and 2 feet deep. There is a 1-foot-wide shelf around the pond, and there is a waterfall about 5 feet high, with four steps. The pond holds 15 koi — four 4-inch fish and eleven 18-inch fish. The pond gets full sun all day.

At present, I use a 4-inch perforated PVC pipe wrapped with foam as the only filter. The wrapping frequently falls off, leaving no filtration at all. I presume this is not sufficient. What do I need for a pond filter? Also, how often should the pond be cleaned and how do I care for the pond while it is being cleaned? Are there any organizations in my area for pondkeepers? I have lots of questions and would like to learn all I can.

A. According to my estimate, your fish load is acceptable by most pondkeeper standards for a pond with a reliable biological filter of sufficient capacity. However, you are courting disaster with the makeshift system that is now in place as a biological filter.

I have several rules of thumb, but the one that applies here is no more than one kilogram of fish per 10,000 liters of water in unfiltered ponds. I estimate your fish total at about 9 kilograms (assuming you measured fish length head to tail) in 5700 liters, so you are at about 16 times over my threshold! The only reason you may not have observed serious fish health problems by now (maybe you have) — such as ammonia poisoning — is because the foam wrapping is acting as a bed for nitrifying bacteria. With a more appropriate-sized biofilter, your fish load would be about 1.6 times my maximum limit, which would be much safer ground.

Properly maintained ponds should never need to be "cleaned," per se. Except for removal of leaves and yard debris, everything else can be removed by partial water changes and flushing of the settling basin or mechanical filter if you have one (your foam-wrapped pipe qualifies in the latter category). When carrying out maintenance, the fish should be left in the pond.

You bet there is a good club in your area — although it is so large the word "club" is a gross understatement. Get in touch with the Mid-Atlantic Koi Club. This is the largest, most dynamic, most active association of pondkeepers I know. The club continues to grow by leaps and bounds and has many local chapters. I have met a good number of the membership and they are enthusiastic, knowledgeable and highly motivated. They will "drown" you in good information. Call their membership directors, Anita and Charles Walker, at (703) 590-3875.