What is wrong with my garden pond?

I built a garden pond on my own three years ago. It is a simple construction made of thick foil. The pond was immediately inhabited by frogs, newts, dragonflies, and even leeches. However, everything seems to die over the winter; in spring I always have to fish out dead frogs from the bottom. On that occasion, I also remove the leaves and add fresh water. During the summer, apparently new amphibians move in again, but they don’t survive the winter with me. What could be the reason? Maybe too little oxygen?

Hi Johannes! How deep is your pond? In order for frogs and other amphibians to survive, the pond must never freeze completely in winter. It must be at least 50 cm deep!

Do you have a lot of leaves in your garden pond? I think there was too little oxygen or none at all. When the bacteria in the pond now want to break down the organic material (leaves), aerobic or anaerobic bacteria come into play. The latter only when no oxygen is available anymore. This process releases foul gases that cannot escape through an ice layer. As a result, the animals are poisoned.

On the one hand, it can be that if there is too much leaves or other organic material in the water, the oxygen is gone here, and there are too many toxins in the water.

And you will not have made the pond only 20cm deep, so that the whole water is frozen, because then your frog can also die.