Mary Allen
Algae in the pond are a nuisance and can sometimes be life-threatening for fish and plants. Many pond owners use chemical clubs to combat algae, but there is another way: Find out here which natural aids you can make your own.
General information on algae
When it gets warmer, the sun shines more often and there is no rain, the risk of algae growing in the pond increases. These never mean anything good, because their appearance is accompanied by numerous negative phenomena; in addition, removing them is a strenuous and time-consuming matter. In the dense carpet of algae, insects can increasingly lay their eggs, as there are excellent growth opportunities for their larvae: a little later, the pond not only looks ugly, it is also populated by a horde of flying (in the worst case stinging) insects.
However, you shouldn’t drive yourself unnecessarily crazy: algae are not immediately dangerous. They almost always appear in smaller amounts and are not harmful at all. On the other hand, they are not allowed to gain the upper hand! That speaks for an extreme imbalance in the pond. In the worst case, it can even be life-threatening for your fish and plants. For example, either because the algae can damage the other aquatic organisms directly (some blue-green algae produce toxins.) Or because they indicate irregularities in the pond that are also dangerous for fish and plants (shifts in water values).
Reasons for algae in the pond
The possible reasons for algae development in your pond can be many, but most of the time they result in an excess of nutrients that develops over time. But so that you can control all possible factors, we would now like to list them all again individually.
Excessive feeding of the fish or too high a stocking density is often to blame for the algae in the pond. In both cases, excess food and a lot of excrement lead to accumulations on the pond floor, which, together with other organic materials, turn into pond sludge. From a water temperature of approx. 10 ° C, the mud begins to release nutrients into the pond water. In addition to fish feed and excrement, dead plant parts, pollen, and organic material from last year contribute to the increased release of nutrients.
In addition, excessive direct sunlight – especially in small ponds – leads to increased algae growth. You should therefore try to darken the pond at least on hot days, for example with a sun sail. Another common mistake is the use of conventional potting soil instead of a special pond substrate. The nutrient richness of this potting soil is easily washed out by the water and also represents algae food.
Another reason is due to the difference to natural waters. These usually have an inlet and an outlet, but this is different with our ponds. Here, water is lost solely through evaporation and inflows only occur through precipitation or the addition of water. During evaporation, however, the nutrients remain entirely in the water, i.e. in the biological system. The number of water decreases, but the number of nutrients. If a few of the reasons listed above are added, the result is quickly an excess.
Possible solutions to the algae problem
More complex, but more effective than the use of algae control agents is of course the complete renewal of the garden pond water. This procedure is very time-consuming because you should never change all the water at once. It is better to proceed on a daily basis and only ever renew certain quantities. This is less stressful for the pond inhabitants and, in addition to algae, not all beneficial bacteria are removed.
If you do not have the opportunity or time to do a complete water change, it can also help to “vaccinate” the pond. To do this, you get water from friends or neighbors from an intact pond that is in biological equilibrium; 10 to 15l can be enough. This “healthy” water is now given into your own “sick” pond. The microorganisms in the good water will then take up their work and begin to destroy the algae. With this variant, however, there is no guarantee of success, it always depends on the individual algae infestation.
A safer option is to use algae-eating fish species. These permanently ensure that algae do not gain the upper hand in your pond. By the way, there are also nutrient-consuming aquatic plants that are especially suitable for extracting nutrients from algae. Last but not least, it helps to fish off regularly occurring algae with the help of a landing net.
Prophylactic measures
You can take action against algae when the pond is not yet filled. When building a pond, you should make sure to create a wide “reed bed” or shallow water zone where the water flows over it permanently. Here, highly nutrient-consuming plants are planted, which – if they are not removed – accumulate excess nutrients in the roots and lower organs. These will then ensure renewed growth next spring.
In addition, the shallow water zone with its leaves and stems offers a large area for beneficial bacteria and other microorganisms, which form the basis for the pond’s self-cleaning power. They are a large part of the biological system, which ideally ensures a balanced water level. The shallow water zone should be constructed in such a way that a pump always lets the water flow through this zone back into the deeper water. This is how oxygen gets into the water and the whole volume goes to this cleaning zone.
Incidentally, it is ideal if you use native plants: These promote a species-rich body of water and are best suited to the microorganisms located here.