The 10 Biggest Myths About Garden Ponds

The 10 Biggest Myths About Garden Ponds and Their Care

Many garden owners want a pond because it invites you to relax and delight with its plants and fish. The decision to create a pond is sometimes made quickly. You create the pond and put plants and fish put in. But when it comes to maintenance, many pond owners have a rude awakening. Newcomers often make various mistakes. Such mistakes are often based on myths surrounding the pond and its care. Several of these myths are at least partially true. To ensure that you have a lot of fun with your pond and do not make such typical mistakes, you should know the pond myths and backgrounds.

1) A Pond Regenerates by Itself

That a pond regenerates by itself is partially correct. A lake is an excellent example to explain this. The plants at and in the water make an essential contribution to the regeneration. Parts of the plants in the shallow water and on the shore zone always die off and rot over time. Similarly, leaves from trees fall into the pond and are decomposed by bacteria. In the process, nutrients are released into the pond water. The animals consume such nutrients in the pond, but also by the algae. This natural decomposition process also leads to the consumption of minerals. Natural rock at the bottom of the lake and on the shore provides for the re-dissolution of minerals and makes them available again for the ecosystem. There is an imbalance between the volume of water and the population of fish. In a lake, a fish can move in several thousand liters of water. If a lake is at least 30 meters deep, an even distribution of temperature zones is guaranteed for all inhabitants. The danger of overheating is eliminated.

In a pond, the situation is entirely different. The pond liner is an insurmountable obstacle for the water. There are no natural sources of nutrient seepage. Since there are no meter-thick sediment layers, the degradation products cannot be utilized naturally. The degradation products accumulate and, over time, poison the climate in the pond. This effect is exacerbated by an overstocking of fish, whose excretions cause contamination. If the dirt decomposition process does not run at full speed, the water will soon tip over.

The pond’s vital substances are used up quickly, but beginners, in particular, forget to top up. There is an imbalance in the system. If you do not intervene, it becomes dangerous for the fish and other animals in the pond. The water can tip overnight, which inevitably leads to the death of the fish.

What you should do:

You should check the water quality monthly and even at least once a week during the warm season. The water values include not only the pH value but also

  • carbonate hardness
  • total hardness
  • nitrate and nitrite
  • ammonium and ammonia.

To maintain the recommended water values and always ensure the correct total hardness, you should regularly add fresh water to your pond or partially replace the water.

2) Clear Water is Also Healthy

The appearance of the water says nothing about its quality and health. Experienced pond enthusiasts can often deduce the quality of the water just by observing it. For accurate statements about water quality, you cannot do without a water test. A strip test is inexpensive and easy to use, but a drop test provides much more accurate values. With a complete set, which costs $20 to $100 (25 to 100 euros) depending on the model, you can reliably check the various water values. You can measure even more accurately with a mobile photometer, which has not been on the market long and costs about $350 (300 euros). With the devices in laboratory quality, you can determine precisely all water parameters. It is up to you which measuring method you choose. Even the expensive laboratory version will be cheaper in the long run than sick or dead fish due to poor water quality.

At a specialized dealer, you can have a water analysis done for money. However, you will only get one-time information about the water values. If you are interested in permanently good water quality, you will have to regularly measurements yourself.

3) A Filter is Needed Only for Large Ponds

Fluctuations in water values occur primarily in smaller and medium-sized ponds, even though water cools or warms more slowly than air. In a shallow pond, the water can quickly heat up to over 86 degrees Fahrenheit (30 degrees Celsius) in summer when the sun is intense at midday. The water can cool just as fast with a fresh, cold wind at night. The fluctuations are favored in most ponds by an excessive stocking density of fish. To ensure that the pond climate remains permanently bearable for all inhabitants, you should not do without a high-quality filter or cleaning system. You will quickly repair damage caused by environmental influences in this way.

If you have a natural pond with a water volume of more than 1300 gallons (5,000 liters), a sizeable deepwater zone, and lush plant life, you do not necessarily need a filter. Even with a large natural pond, you should not forget to check the water values regularly. In a natural pond, you should only put small fish species such as minnows, bitterlings, or moderlieschen. These fish are content with the raw food supply of algae and insects. Since they are native fish, they are hardy. Even frost cannot harm them. However, it would help if you did not forget bubbling stones or a circulation pump for good aeration.

4) You Can Turn Off The Filter

Turn off the filter in the meantime. You save electricity and do not disturb the neighbor with the water noise. If you are not at home, the hose cannot come off, and the pond cannot run empty. From a biological point of view, it makes absolutely no sense and is even counterproductive to run the filter only by the hour. If the filter is only in use by the hour, the effect is even less than without a filter.

The functioning and the structure of the filter make it clear how important it is to run the filter permanently. In the first filter stage, the filter captures dirt and waste materials. In the second filter stage, bacteria convert these toxins and debris into non-toxic end products. For this to be possible, the bacteria require vast amounts of oxygen. The oxygen demand of the purification bacteria is sometimes more significant than the need of all fish together. In some cases, it takes several weeks for this process to run reliably and stably. With actively dosed live bacterial preparations, the process of breaking down sediments and pollutants takes only a few hours or days.

If you switch off the filter only once for about 30 seconds, the bacteria can only work until the stagnant water’s dissolved oxygen is used up. As the bacteria then die, a chain reaction occurs so that the nitrogen cycle goes backward and the water quality rapidly deteriorates. In the absence of oxygen, non-toxic nitrite is converted into highly toxic nitrate. The die-off process accelerates because the bacteria can break down nitrate but cannot tolerate large amounts of it. If you turn the feed pump back on, the dead bacteria and nitrite are flushed back into the water, which is too much for the fish’s delicate immune system.

As the heart of the pond, the filter must be regularly supplied with oxygen and the fish’s excretions. If this system is disrupted, algae will build up more. Your fish will become sick and may die.

5) Rainwater Does Not Harm

If rain falls into the pond in the usual way, it is not a problem. Control and correct the water quality regularly, and you will not harm the ecosystem. However, some pond enthusiasts capture rainwater or direct it into the pond through the gutter to perform regular water changes. They argue that in nature, rainwater also enters bodies of water.

The situation is quite different with your garden pond. The raindrops pick up various dirt particles in the atmosphere. As the rainwater runs over the roof into the gutter, various debris such as dirt, moss, or leaves is washed into the pond water. This causes many substances to enter the water, which is a perfect breeding ground for algae. Rainwater also does not contain minerals that are necessary for the pond water to maintain its self-cleaning ability. If you pipe rainwater into the pond, you must constantly check the water values and compensate if necessary. In the long run, this becomes quite expensive and time-consuming. Pre-purified tap water is best. It would be best if you had a water conditioner, but you will need to use it less often than with rainwater.

6) Care Products Harm Because They Are Chemical

Many pond owners say they don’t want to use chemicals in their pond. The pond care products offered in the 1980s were mostly based on chemicals. These products only served to kill the algae spores and clarify the water. However, in the process, beneficial microorganisms were also killed. Fortunately, the trend has been towards a natural way of life and biological balance for some years now. The industry responds to customers’ ever-increasing desire for biological means and the laws protecting nature and is launching modern preparations that support the biological process.

The new algaecides and care products are mostly made of natural substances, which provide a biological balance when there was an imbalance between dirt input and dirt removal. The main ingredients of these care products are usually copper sulfate and monolinuron. As an essential building block of life, you found copper in many foods such as fish, meat, walnuts, vegetables, and coffee. The German Federal Office for Risk Assessment even recommends a daily copper intake. Fish feed for goldfish and koi is often supplemented with copper to prevent deficiency symptoms. Copper in a slightly increased concentration is dangerous for sensitive algae and leads to their death.

Calcium and bicarbonate are used to correct natural water parameters such as pH and water hardness. Products for algae prevention are also produced on a mineral basis. The basis of sludge removers and filter boosters is purification bacteria.

7) Feed Is Feed

Why buy high-priced feed when cheap feed is available? The answer is simple. In the long run, the expensive meal becomes cheaper. Feed-in the higher price segment is produced based on protein, which leads to higher costs. Protein is an essential building block of life. It makes you complete and gives you energy.

Food for goldfish and koi is primarily offered in the form of pellets or granules. 34 oz (one liter) of pellet food can contain ten times the amount of energy of slurried cheap food. Cheap food is often available as sticks.

Instead of a shot glass full of pellet food, you would need to feed four hands of sticks daily to keep your fish full. Since the high-protein pellet food is almost completely utilized, it also makes itself felt less excretion from your fish. This leads to fewer algae in the pond. You need fewer maintenance products and have to clean your pond less often. Your fish are healthier and present themselves in a more beautiful blaze of color.

There are feeds specially adapted to the seasons because your fish’s energy requirements differ depending on the time of year. You should therefore pay attention to the water temperature information on the packaging of your food.

8) Fish Food Contains Enough Vitamins

High-quality fish food is offered in opaque packaging. When exposed to light and air, the vitamins oxidize quickly and are no longer available as valuable ingredients. Open the package, and you set the oxidation process in motion.

To provide your fish with enough vitamins, you should think of drops or spray for revitalization. In the ornamental fish or pond department of a good specialty store, the professionals can advise you on which vitamin preparations are suitable for your fish.

You can avoid many fish diseases by boosting your fish’s immune system. An intact immune system has a particularly positive effect on the thickness of the mucous membrane, color development, and stress resistance in water problems. Store your vitamin supplement in a cool place, and it will last you at least one pond season. In the spring, parasites kick into gear as water temperatures rise. The metabolic system of the fish is activated. Especially at this time, you should not do without vitamin supplements. You can give the vitamin preparations directly into the pond water, but you can also dose them via the feed portion. When dosing directly into the pond, the vitamins are absorbed by the fish via the mucous membrane and the gills. It would be best if you gave vitamins three to four times a week in spring, while in summer, one vitamin dose per week is sufficient.

9) Fish Adapt to the Size of the Pond

If you think fish can adapt to pond size, you’re wrong. Many pond lovers are blown away when they see colorful koi in the pet store and can’t resist. It would be best if you did not forget that a koi can grow over 3.3 feet (a meter) long and needs a corresponding amount of water. Fish cannot adapt to the environment with a control function in their growth.

If the fish in your pond remains minor than the fish of the same species in your neighbor’s pond, it is somewhat due to the conditions in your pond. If the pond is only small or medium in size and the stock density is too high, vitamins, minerals, and other growth-promoting substances are quickly depleted. The fish release growth-inhibiting substances into the water through their excretions. The formation of algae is promoted, and the existing plants cannot sufficiently complete the decomposition of toxic nitrate.

If the fish in your pond does not have enough room to move, digestion and metabolism are not sufficiently promoted. If the fish remain small, this is not due to the adaptation of growth to the habitat but malnutrition and poor development.

You should only buy the fish if you are sure that you can offer them the optimal conditions in your pond. The rule here is: less is more. If the fish population is only small, the fish can move well, feed, and develop species-appropriate.

10) Koi Are More Sensitive Than Goldfish

Koi and goldfish are similar in anatomy and have identical water quality requirements. It is not true that koi are more sensitive than goldfish. Koi only have higher demands on space and feeding. Koi are often not kept in a species-appropriate manner. As a result, they suffer from deficiency symptoms and become ill. Such diseases are often not recognized early enough to be treated. As a result, the fish die.

Koi have a high energy requirement and increased metabolism. You should always pay attention to high-quality food and also give your fish enough vitamins.

A koi needs approximately a water volume of 1,300 gallons (5,000 liters). Koi are not solitary animals. Since they are group animals, they get bored when they are alone. They feel comfortable in a group with three to four animals. You will need about 265 gallons (1,000 liters) of water for each animal. For a group of four fish, you need a volume of 2,113 to 2377 gallons (8,000 to 9,000 liters) of water.


There are numerous myths surrounding garden ponds and their care. To enjoy your pond and your fish, you should know the background of these myths. It would help if you remembered that the pond could not regenerate completely. You should check the water values regularly and compensate if necessary, and you cannot do without a filter. The filter must be in use around the clock to ensure that there always is a biological balance. It would help if you did not compromise on quality when feeding your fish and provide your fish with sufficient vitamins. The space requirements of the fish are also essential.

The excretions of the fish speak for themselves. Even a koi that is only 8 inches (20 centimeters) tall will excrete about as much feces as 30 to 50 goldfish of that size. You must adjust the filter to the number of fish and regularly check the water values to reduce the germ load. If you follow all these principles, a koi in your pond can reach a length of 4 feet (120 centimeters).

Florian Egert

I am Florian Egert, the owner of I live with my wife and two children in Germany in a small village in the countryside.

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