Creating an underwater garden full of lush plants and beautiful, healthy fish often intimidates aquarists. However, it's actually not difficult; it simply requires understanding and familiarizing oneself with the basic relationships and processes occurring in a closed underwater ecosystem. Every plant requires optimal light, water, and substrate parameters to thrive. Each of these parameters can either stimulate or inhibit growth, so maintaining the proper balance is crucial.
Light and Plant Photosynthesis. Photosynthesis is one of the fundamental biochemical processes in plants, during which energy-rich chemical compounds are produced using absorbed solar energy. The goal of the reaction is to produce a molecule that can store energy. During photosynthesis, the H2O molecule breaks down, and oxygen atoms are released into the environment in the form of O2 molecules. Glucose is the first product of photosynthesis and can be converted into other compounds that are crucial for plant growth and development. Factors influencing the intensity of photosynthesis include: CO2 concentration, ambient temperature, and irradiance, and photoinhibition. In the absence of light, plants release CO2 produced during cellular respiration. At very low light intensities, CO2 release during cellular respiration outweighs photosynthetic CO2 fixation, and the plant continues to release carbon dioxide. At a certain light intensity specific to the plant species and prevailing conditions, CO2 uptake during photosynthesis and CO2 release during respiration are equal. This point is called the light compensation point. At light intensity above the light compensation point, photosynthesis increases. At a certain light intensity, specific to each plant, photosynthesis becomes saturated with light. At this point, photosynthesis begins to slow down due to the phenomenon of photoinhibition. In short, light intensity accelerates plant growth, but only up to a limit.
Physicochemical properties of water. Water, the world's best solvent, carries not only basic elements such as potassium, nitrogen, and phosphorus, but also a number of elements that plants require only trace elements. In nature, elements enter water bodies from precipitation, surface runoff, and other river inflows. Without both macro and micro elements, our plants will not grow and look healthy. Macro elements are elements that constitute at least 0.01% of the dry weight. These include so-called biogenic elements, meaning those that play a key role in plant structure, photosynthesis, and the Calvin cycle. Other micro elements also play a key role, including in color development. Plants require appropriate nutrition, provided in a digestible form and in proportions appropriate for the species.
Each plant species has different nutrient requirements. Once a plant's supply of a given mineral is depleted, it initially exhibits deficiencies and then dies. An appropriately balanced ratio of trace and micro elements must be constantly maintained because both excesses and deficiencies can inhibit plant growth.
Substrate. Substrate plays a key role in a planted aquarium. It is where individual processes of compound transformation occur, which can later be absorbed by plants. Substrate buffers excess compounds contained in the water. It also acts as a source of trace and trace elements for our flora. For root plants, a symbiotic relationship between plants and bacteria occurs in the bottom layers. In our closed-ecosystem aquariums, fish excrete metabolic waste, and it is in the substrate that nitrogen is converted from an indigestible form into one that can be absorbed by aquatic plants, primarily in the form of nitrate anion NO3- and cation NH4+. Therefore, it is important to avoid anaerobic zones in our substrate, where plant root rot can occur. Furthermore, the lower layer of the substrate should have a structure that facilitates and stimulates the growth of aerobic bacteria living in symbiosis with the roots. A good substrate in an aquarium will act as a filter, a storage for toxic compounds, will stimulate symbiosis between the plant and microorganisms, and will regularly supply plants with macro and microelements.
Plants. It would be difficult to imagine an aquarium without aquatic plants. Aquatic plants have a huge impact on the appearance of a water body. They can give the tank its unique character. Plants allow you to perfectly compose any tank and recreate a natural biotope. The decorative and decorative role of aquatic plants is undeniable, but they serve a much more important function. They help maintain biological balance in the water body, and thus the water's ability to self-purify, serving as a fundamental component of the regeneration zone. A properly functioning ecosystem in a planted aquarium supports and maintains water parameters at a constant level, while also being responsible for the water's appearance (crystalline, clear). Proper plant growth significantly limits the growth of algae and cyanobacteria, eliminates dangerous bacteria, removes toxic compounds from the water, and creates optimal conditions for fauna to thrive. Knowing the basic plant growth stimulants, discussed briefly above, we should select plants for our aquarium, ensuring they have similar requirements for temperature, pH, and hardness. We must also be aware that as light intensity increases, we must provide the plant with nourishment to thrive. The better the substrate, the greater the buffer for our errors. In our aquariums, we must closely monitor plant development and carefully respond to individual deficiencies by dosing appropriate fertilizers.
The topic of mineral nutrition for plants, lighting and water has not been exhausted and we will probably return to it many times.