Humic substances are natural derivatives of organic materials found in soils and, more importantly (for aquarium hobbyists), in many forested streams and rivers. They are collectively comprised of humic and fulvic acids, which are the product of the natural decomposition of proteins, carbohydrates, lipids, and lignins of plant and/or animal origin. A characteristic of humic substances is their deep brown color, which is responsible for the color of soil. Soluble humic substances increase the bioavailability of multivalent cations (many of which are important nutrients for plants) to plants considerably by forming temporary bonds with these ions and making their uptake by plants more direct; this increases the effectiveness that water care products containing these ions will have in planted aquaria. Blackwater rivers are so-called because of the coloration of the water, which ranges from light- to dark-brown (as a result of the presence of humic substances), but is transparent. There are many important blackwater rivers in iver drainages, as well as throughout forested regions of Southeast Asia, all origins of many families of important aquarium fishes. Blackwater biotope aquaria are therefore desirable when attempting to maintain these fishes. Gradually increasing the concentration of humic substances in aquaria is an effective method of encouraging spawning in fishes, particularly for Discus, Cardinal Tetras, and other inhabitants of such blackwater rivers as Brazil’s Rio Negro. In general, the concentration of humic substances increases substantially during periods of excessive precipitation and/or flooding (e.g. “rainy season”), which is also when fishes in many river systems spawn. The addition of Brightwell Aquatics BlackWater to an aquarium will slightly acidify the water, and will discolor it in direct correlation with the dosage used, the volume of the water in the entire aquarium system, and the method(s) of chemical filtration employed; in general, the greater the dosage employed, the more pronounced the change in water coloration will be. BlackWater will also soften water as a result of the natural chelating action of humic substances. These are all important environmental and/or chemical cues utilized by fishes for the onset of spawning.