In nature, black water is extremely soft and acidic water. The conductance is less than 10 µS/cm, the pH value is less than 5.
Blackwater has no detectable carbonate hardness. The water therefore does not have a carbonate buffer like our tap water, which buffers the pH value. In black water, the buffer system is formed from weak organic acids that are produced when parts of plants that have fallen into the water rot. The pH value in such waters can drop to around 3.4 and remain stable at the same time. Due to the large amounts of plant parts, the water is often colored a deep dark brown.
Do fish need black water?
A number of tetras and other fish species originate from blackwater rivers. Of course, these tetras feel particularly at home in black water. The important thing is not so much the dark color but the water hardness, the pH value, etc.
Fish that absolutely need black water do not normally make it to the pet store alive in the first place.
A number of fish species naturally live in extremely soft and acidic water, but do not necessarily need this water to survive. However, some of these species require such water for breeding.
Species-appropriate water for such fish is best produced with the help of reverse osmosis systems and peat or something similar. However, care must be taken when producing extremely soft and acidic water. Due to the low carbonate hardness, the pH value can very easily drop too much and an acid drop can occur. The stability of the water may be given preference.
Fish from soft water areas should not be kept in black water. In principle, only fish that require at least very similar water parameters should be kept together. Therefore fish from black water areas should not be kept in normal water.
Generate black water by adding water?
Many manufacturers have products in their range that supposedly turn tap water into black water. However, these agents do not produce black water in the biological sense, only colored water. Depending on the agent, the water is enriched with hydrochloric acid. Blackwater extracts usually color the water. Other products such as pH/KH-Minus and pH-Plus change the corresponding water values.
However, these remedies are only helpful for a short time or in small aquariums. When used sparingly, no black water can occur. With generous use, the pH value drops, but the conductivity increases, so that no black water is produced again.
Products for the production of black water
Means for the preparation of black water should be used carefully. As a rule, the ingredients and their concentration are not specified exactly. Some of these agents contain inorganic acids such as hydrochloric, sulfuric or phosphoric acids or similar additives. So the application is not without risk. It is often safer to work with pure acids, since the exact concentration is then known. Some agents, such as , increase the phosphate content in the water and thus increase the risk of algae.
Other remedies, such as Sera Morena, do not appear to affect phosphate levels. On the other hand, peat and peat extracts have a slight algae-inhibiting effect. Alder cones also have the same effect.
blackwater concentrates
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