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Old Pond Tales

How accurate is that piece of advice you heard over the backyard fence? Ove veteran pond-keeper investigates.

by Rick Gush

Graystone creations john olson

Photo taken by: John Olson -

One of the most frustrating experiences for a pond owner can be receiving advice. Pond-keeping is a complex endeavor, but most advice seems to be brutally simple truths, dispensed with great authority. Drain annually! Just use salt! It’s easy to feel a bit confused and ignorant in the face of such elegantly simple rules. How could we have missed such obvious facts in our own research?

People love to give advice, and the less complicated and more profound the advice, the smarter the counselor will appear. Advice that includes a long list of maybe this and maybe that seems weak and uncertain in contrast to short pearls of wisdom. But the fact is that there are very few magic answers. All old pond sayings have a long series of equivocations and exceptions that go along with them. Surviving in the world of pond-keeping is greatly helped if you understand the kernel of truth in any bit of popular wisdom, and also know something about the possible exceptions and equivocations to the rules.

The secret seems to lie in being open to new bits of information but at the same time trusting yourself and your own acquired knowledge and observation. Even if you're a beginner on your very first day, you have received information about ponds and fish for years and probably know a lot more than you think. You are your own pondmaster, and the panic that arises from thinking that "Everybody knows more than I do!" will lead only to bad decisions. The only way to know who and what information to trust is to first trust yourself.

Read these Old Pond Tales and find out how much truth lies in each.

Fish Tales

Tale: You must have 3-foot-deep ponds to keep koi.

One of the most common pond tales is that a pond needs to be at least 3 feet deep to keep koi. This probably got started because ideally a koi pond would have great depth, but the fact is that some pond-keepers manage to raise koi in 1-foot­deep ponds. Sure, these people probably live where the winters are warm, and they probably have nice plant or structural cover for the fish to lounge in the shade, and they probably have a pretty good aeration system that keeps the oxygen levels high.

A 2-foot-deep pond could hold koi during a Wisconsin winter, because the fish could theoretically survive in the water under even a 9-inch ice layer, although adding a freeze prevention heater and circulating pump would be nice.

Of course, the old pond tale contains a great deal of truth. A shallow pond is more subject to fluctuations of chemistry and temperature -both of which can be deadly to fish. So, if you were that koi, wouldn't you prefer that your considerate owners kept you in a luxuriously deep pond rather than in a shallow pond that is potentially precarious? It's not hard to see who started the 3-foot-deep rule: the fish.

Truth: Three feet of depth will save your koi from temperature and chemical fluctuations, and predators, but in certain situations isn't absolutely necessary.

Tale: You cannot keep both koi and plants.

Pond owners often say that koi will ruin any pond plantings, and should stay in plant-free ponds. True, koi do frequently dig up some plants and eat others. It does seem to take a reasonably long period of trial and error before a nice planting is established in a koi pond. A new pond, with new plants and new fish, will certainly experience several incidents of plant destruction and muddy water before achieving a harmonious balance.

But phooey! Just because it's hard and takes a considerable effort is no reason to abandon the idea of a lushly planted pond with monster koi swimming happily in the sparkling water.

The secret is, as usual, to trust yourself and your own observations. Certainly you have seen ponds and photographs of ponds in which koi and plants were in harmony. So, you can be sure that such an effect is possible also in your own pond, and that achieving that state may just require that attribute in which some people are classically deficient: patience.

Truth: Through trial and error, both koi and plants can live together in harmony.

Flora & Fauna Fables

Tale: You can't have a pond without plants.

A common prejudice holds that any good pond has a lot of nice plants. From a fish's point of view, plants are highly desirable, as they offer hiding places and perhaps dietary benefits. As one of the key components of an ecosystem, plants are heavyweight contributors. For most of us, the plants are a huge part of the pleasure of pond-keeping. Creating a lush retreat is our goal, and our little world wouldn't seem right without plentiful plant growth, in and out of the water. Even the fashionistas who restrict themselves to one strategically placed plant in a pot will glory in the exuberant growth of their specimens.

But, no, plants aren't absolutely necessary. This may seem to be a question of taste and fashion, but there are in fact some good reasons to avoid plants in ponds. Eager fishkeepers often dispense with plants because visible fish can be controlled and handled for disease evaluation more easily, and breeding and pond change is less traumatic to fish unaccustomed to hiding. This pond wisdom was certainly first circulated by an intelligent pond keeper, and it is only in the severity of the application that the rule errs. Sometimes there are good reasons to break a rule.

Truth: Easy water changes and happy fish could result from a plant-less pond

Tale: Wild animals will prey upon your pond.

Some prospective pond builders fear that four-legged predators like raccoons, and two-legged predators such as herons will swoop down on an unprotected pond and eat all the fish. There is more than a grain of truth to this fear, as fish in small ponds near woodlands or wild areas are easy prey for predators. If you live where herons do, expect hungry visitors. Raccoons are less common pond predators, as they don't like to swim, but a small shallow pond is not much of an obstacle for these scavengers.

Motion-detector-triggered systems that move scarecrows or spray jets of water are possible solutions to a severe heron problem, and a well-planted pond with plenty of cover in which the fish can hide is a good defense against all predators. This rumor about the inevitability of predators was probably started by a cardiologist who had a beautiful pond built for his mountain cabin and watched the osprey lunch on his imported koi.

Truth: You can fight off predators with a few simple methods.

Tale: Mosquitoes will breed like crazy in your pond.

Ponds used to be common breeding grounds for mosquitoes, and many people continue to think ponds are still generating millions of potentially dangerous "skeeters." Unfortunately, some truth exists to this way of thinking. Neglected ponds, abandoned ponds and, casual flood ponds can all be active mosquito-breeding sites. But these days, civic agents in every state patrol to seek out such potential hazards, and the number of mosquito-breeding ponds has diminished greatly in the last several decades.

Well-kept ponds almost never breed mosquitoes. Moving water, hungry fish, pond filters, and occasional plant prunings keep mosquito incidence to a minimum in almost all backyard ponds today. Nonetheless, this rumor about mosquitoes and ponds is still propagated by some worry warts.

Truth: Well-kept ponds make poor mosquito breeding grounds.

Tale: You'll get warts from toads around your pond.

An even more ancient superstition concerns warts and toads. It is surprising how many people, even in these enlightened times, do not want to touch toads because they believe they might get warts as a result. Ha! Medical doctors and animal biologists can guarantee that whoever picks up a toad will not get warts.

Toads are great pond inhabitants. They have an amazing insect eating capacity and add woodsy charm by occasionally being seen moving among the foliage.

Truth: Toads make great pond inhabitants.

Water Wisdom

Tale: Vinegar will keep pond water clean.

People are somehow attracted to advice that makes use of common household products. Two examples are the ideas that vinegar can be used to lower the pH in a pond, and that baking soda can be used to raise a pond's pH. As usual, there is a bit of truth in these concepts. Unfortunately, the use of vinegar can actually cause problems. While vinegar is an acid, it has many bad effects on a pond, such as irritating fish gills, adding to the organic waste load and increasing bacterial activity. Besides all that, vinegar is so weak an acid that it would take 4 gallons to equal the acidifying capacity of a shot glass of hydrochloric acid.

Baking soda is actually much more appropriate as a water treatment, particularly in those few areas of the country that do not have a high carbonate content in the water. In addition to raising the pH, baking soda is a buffer that prevents quick pH swings. So, sometimes yes, and sometimes no, household products can be used in pond maintenance. But still; specific pond store chemicals will carry the backing of the manufacturer. Pity the someone who decides to use laundry chlorine to treat a fish fungus.

Truth: Vinegar can do more harm than good.

Tale: Water testing is required

Is water testing really required? This testing idea is well entrenched in the basic information of all the major pond advice sources, and pond water testing kits are staple items at pond supply stores. But is all this testing really doing any good? As usual, the answer is yes and no.

Yes, testing is a good way for a new pond owner to see what sort of changes are going on as the initial balancing of the pond water chemistry takes place. Testing can show if some parameters are way out of line and require corrective action. In the early stages of a pond, daily testing can be quite informative.

But daily testing can be a real pain after a while, and if after a few months a new pond is not settled down to a reasonable balance, the owner is probably overdoing their chemical applications. Old pond owners may not test for long periods of time because they don't need the information.

Truth: Daily testing is not necessary far established ponds, but occasional tests can be illuminating.

Algae Adages

Tale: All algae are bad.

A widespread notion suggests that algae in a pond is bad but that thriving pond plants will out-compete any algae and clarify the water. Actually, algae are beneficial, mainly because many fish and many small pond inhabitants eat them. Too much algae is what's bad, and that is caused by too much sunlight or too much available nutrition, likely from excessive amounts of decomposing plant material. A few shade trees and some broadly leaved pond plants can solve the sunshine problem, and a regular brush cleaning can solve many excess nutrition problems.

Plants won't out-compete algae, but they can dramatically reduce the available nutrient load of a balanced pond. It is true that plants can shade algae, but who wants a pond with the whole surface covered by plant growth? If there are some big, sunny patches uncovered by leaves, the algae in the whole pond will grow according to the nutrients available. This misconception that all algae is bad was likely started by a pond owner frustrated by some particularly heavy algal blooms, which can happen to any pond owner once in a while.

Truth: Some algae can be beneficial

Tale: Using ultraviolet lights will clear a pond of algae.

We're all a bit dazzled by technology these days, and even a relatively old practice can seem like whiz-bang science. This feeling paves the way for the frequent assertion that ultraviolet-light water sterilizers are the best way to maintain crystal clear water. No doubt, UV can effectively control some algae types; although UV treatment does not actually sterilize water, it does destroy many potential pathogens.

But, UV is expensive, and it can actually backfire if too many dead algae drop to the pond bottom and feed an even bigger algae bloom. String algae are unfortunately not controlled at all by UV treatments. UV lights are most helpful in controlling algae blooms in new ponds that are as yet unbalanced, but once installed, most people keep using them, at least until they get tired of the annual bulb replacement costs.

Truth: Beneficial, especially for new ponds, this treatment can become quite expensive.

Homeowner Pond Myths

Tale: Concrete is toxic to fish.

Homeowners are sometimes too enthusiastic about their backyard projects, and they rush things a bit. Without a doubt, this is how the idea that concrete is poisonous to fish got started. Fresh concrete is indeed toxic to fish because it is highly alkaline, and the water in a fresh concrete pond can spike over a pH of 9. This means that the water would corrode most anything that sat in it for awhile. Pity the poor fish dumped into a pond that the homeowner finished last weekend and just filled yesterday. A new concrete pond needs to be cured with a week or so of acid treatments (acid added to a filled pond every day) before either fish or plants are added.

Truth: After the concrete cures, it's safe for fish.

Tale: Hydrochloric acid is toxic to fish.

This myth is just plain not true. Muriatic acid, also known as hydrochloric acid, is the inexpensive acid most often used for swimming pools and, used in small quantities, the best pH-lowering acid for the many alkaline water areas in the country. Sure, dumping a load of muriatic acid in a pond might cause a quick and massive drop in the pH (which is very bad for the fish) if the carbonate hardness of the water is low, but large amounts of any acid could theoretically cause the same effect. Perhaps an overeager. acid doser fried his koi and then started this myth about muriatic acid's toxicity.

Truth: Overusing any acid is detrimental

Trust Thyself

For many different reasons, popular wisdom takes form - some with a solid base of facts, and some with little or no factual base at all. In the end, the safest course for a pond owner is to steer a skeptical but interested course, skeptical of any miracle cures, but interested in finding the core of truth in any advice. Pond owners must learn to trust their own instincts and be patient. It is amazing how quickly a cloudy pond can clear once it calms down, and it is quite satisfying to know that your own wise management skills help harmonize this little ecosystem called your pond.

Farm and garden writer Rick Gush lives in Rapallo, Italy.