Dried alder cones.
These little cones release tannins and humic acid.
They have an antibacterial and fungicidal effect. Furthermore, they bind copper, iron and heavy metals.
These cones slightly acidify the water and lower the pH, GH and KH.
Recommended dosage: 1-2 cones in 20 liters of aquarium water for about 2 weeks.
Size 1-2cm