Preventive measures against algae proliferation.
Correct aquarium placement. The aquarium should be positioned so that it is not exposed to direct sunlight. Sunlight provides too much energy for plant metabolism; plants absorb excessive nutrients in a relatively small volume of water, which immediately demands increased feeding and consequently slows down growth. Algae will thus gain an advantage.
Check plants before planting. Do not acquire any aquarium plants from tanks where algae are present. Carefully inspect plants before placing them in the aquarium. Check for any signs of algae contamination. Preparing potted plants for the aquarium. Aquarium plants purchased in pots are mostly grown in nurseries. The leaves of the plants were above water, while the roots were submerged in a special nutrient-rich solution that may contain a lot of nitrates and phosphates. In most cases, this nutrient solution is not completely washed out of the substrate in which the plant roots have grown. Therefore, plants must be thoroughly separated from pots and substrate by rinsing with lukewarm water before planting them in the aquarium.
Proper water management and regular water changes. Optimal supply of all necessary nutrients to aquarium plants, including 
trace elements, is a prerequisite for beneficial growth while protecting against algae. Well-balanced macro- and micro-element fertilization eliminates the danger of overdosing—especially considering the toxicity and lethality to plants of overdosing many trace elements, which would once again give algae the advantage. Regular water changes ensure the removal of harmful substances and various wastes from the aquarium.
Everything dissolves in water, turning it into a nutrient medium. The question is: for whom? If the lighting is inappropriate, free carbon dioxide is scarce, the temperature is too low or too high, and nutrients are in excess, then you are running an aquarium for algae. That is what will grow in it. If there is a nutrient medium, someone will definitely feed on it. And it will be the organism for which it is best suited.
pH adjustment via CO2 injection. Regulating water pH to neutral values (6.8 to 7.2) is maintained not only for optimal carbon supply to plants but also for a favorable chemical environment in the water. It is known that most algae thrive better in hard water with high pH values. Hence the recommendations aimed at lowering pH. This is achieved by adding strong acids to the water, which in some cases yields positive results, but far from always. Sharp pH fluctuations can negatively affect fish and plants. Furthermore, the water pH rather quickly returns to its initial value.
Lighting selection. Aquarium lighting must correspond to the height of the aquarium and the water volume. The light source must be powerful enough to provide sufficient light even for the smallest plants at the bottom of the tank. Too strong light will quickly lead to a shortage of nutrients, especially trace elements. This will again lead to algae dominance. Too weak light, in turn, leads to a cessation of growth and oxygen deficiency. The right lighting must be chosen between these extremes.
Plants do not need just any light for photosynthesis. The intensity and the specific emission spectrum of the lamps illuminating them are extremely important. A sign of trouble is simple: if a brown coating grows even in well-lit areas, there is not enough light. It burns to the benefit of diatoms, whose photosynthesis occurs in a different part of the spectrum and at a different intensity. The lamps need changing. If you observe the opposite—the leaves of higher plants turning edge-on to the light instead of flat, or folding up to close the apical growth point and young leaves at the top—it means there is too much light. This is usually accompanied by the proliferation of green algae on glass, stones, and the leaves of higher plants.
A shift towards the blue part of the spectrum strongly promotes the growth of algae such as *Audouinella* (black beard algae). *Audouinella* also loves stray light from windows during long days. Higher aquarium plants originate from the tropics, where day length does not vary as widely as in the temperate zones of the Earth. The photoperiod cannot exceed 12 hours. During a long aquarium day with low-intensity lighting, algae gain a significant advantage over higher plants because they can grow and feed during the period when higher plants lack photosynthetic activity.
An indicator of correct lighting is the appearance of a moderate amount of green algae (dark green patches consisting of relatively stiff filaments) on the glass and older leaves of plants. If they are absent, the aquarium is poorly lit or the light spectrum is wrong. The appearance of a green coating or small brush- or hair-like patches of green on leaves and glass indicates excessive lighting. Placing floating plants on the surface creates an excellent light filter for many plants requiring shading and reduces the light flux when necessary. You can protect the lower tier from excessive light by planting large bushes of sprawling, light-loving plants or stem plants.
People often make the mistake of reducing light intensity or duration in an attempt to curb algae growth. But instead, this stunts plant growth and further exacerbates the problem. Healthy plants help suppress algae growth by competing with them for available nutrients. If it becomes necessary to clean algae off the display glass every few days, it means algae are growing too vigorously. This phenomenon occurs when there is an excess of nutrients.
If algae become a problem, it is a sign of high nitrate or phosphate levels caused by overstocking, overfeeding fish, or inadequate water changes. This, in turn, may be due to excessive doses of aquarium fertilizers meant to accelerate plant growth, though it is most commonly an indicator of poor aquarium maintenance.
A thick substrate layer increases the production of methane and hydrogen sulfide gas. The consequence is a reduction in oxygen. The correct substrate layer is 3 to 7 cm (depending on 
the size of the aquarium). Algae are more likely to appear on a sand substrate than on gravel. Heavily infested areas should be removed from the water. Algae love it when many substances are dissolved in the water, whereas higher plants do not. The nutrient medium for higher and lower plants in the aquarium is formed in the harmony between these two factors.
High concentrations of nitrogen salts, phosphates, other fertilizers, and protein breakdown products in the water inhibit the development of aquatic plants and stimulate the mass proliferation of algae. Therefore, if you decide to fertilize your planted tank, apply the fertilizers into the substrate, closer to the roots. Bury dry fertilizers, and inject liquid solutions using a standard medical syringe. Only trace elements should reasonably be added to the water column. However, it must be remembered that plants need trace elements in micro-doses. An excess of trace elements accumulated in the aquarium through regular fertilization greatly stimulates the development of certain algae, such as green filamentous algae.
Temperature. Higher plants in an aquascape originate from the tropics and love warmth. Most cannot tolerate a chronic temperature drop below 20-22°C. Higher temperatures increase metabolic rates. If anything is lacking, decompensation, exhaustion, and death follow. Higher plants wither and die, while algae and bacteria rejoice and multiply.
Algae-eating fish as a preventive measure. An effective measure against algae is keeping fish that like to feed on them. There is a wide range of choices. Several fish species eat algae: *Ancistrus*, *Gyrinocheilus*, *Crossocheilus*, *Poecilia reticulata*, *Epalzeorhynchos kallopterus*, *Labeo*, *Xiphophorus helleri*, *Morulius*, *Otocinclus*, *Poecilia sphenops*, *Farlowella*, *Helostoma temminckii*, *Epalzeorhynchos*. Filamentous algae are eaten by mollies (*Poecilia sphenops*), and other fish species often follow their example and start eating hair algae as well. However, this does not provide a 100% guarantee, as these fish quickly realize that dry and live foods are much tastier.
Blue-green algae, Cyanobacteria, Blue Green algae (BGA).
Algae – unwelcome guests of the aquarium. 
