The barley straw reactor uses a process that is mainly used in ponds. Barley straw bales are placed in ponds to prevent excessive algae growth. Corresponding extracts can be found in the garden departments of DIY stores or in garden centers. The dosage must be calculated down to the size of the aquarium. BioFerm from JBL works according to the same principle.
It is unclear which substances from barley straw are effective against algae. It is assumed that lignin plays a role. Because lignin is the second most common substance in plants after cellulose, other substances are probably also involved, or the composition of the lignin is decisive. Otherwise practically every plant would be effective against algae. Lignin is composed of various other components, the exact composition of which differs in different classes of plants.
Although there are aquarists who put barley straw directly into the aquarium, the method is risky. Barley straw rots like other dead plant material, adding additional pollution to the water. Therefore, breeds for parameciums are set up with straw. after a week of straw in the water, a stinking broth develops, in which, however, masses of paramecium thrive. It is therefore important to only use enough straw so that the water pollution does not increase and an effect against algae is still achieved.
Sawdust can also be used as an inexpensive replacement filling. Since the exact mode of action of barley straw is unclear, it is not clear whether sawdust from all types of wood is suitable.
Aids such as barley straw only ever treat the symptoms. It makes more sense to determine the causes and eliminate them. As a temporary measure to combat algae plagues, however, it can make sense to use barley straw.