What is needed to create an underwater garden.
It is essential to remember such a characteristic of the substrate as color. Ideally, the aquarium substrate should be dark – black, gray, brown, or dark red. Against such a background, plant greenery and the bright coloration of fish will look significantly better. When choosing substrate color, one should keep in mind that dirt and algae growth are more noticeable on a light background than on a dark one. A light substrate requires more thorough cleaning and needs to be stirred more frequently.
Many manufacturers of aquarium accessories offer artificial substrates: dark, light, multicolored – made of brightly colored pebbles, manufactured from small rounded glass or plastic particles and spheres. It comes in a wide variety of colors, and multi-colored mixes are also produced. Their use can be interesting for decorative purposes. You can use it if you want to make the aquarium motley and do not strive to create a natural aquascaping style.
Plastic-coated colored gravel, due to friction inevitably arising from substrate disturbance and contact with water, as well as fish digging in it, can gradually wear down, causing the base material to directly interact with the water. In addition, plastic tends to degrade and lose its qualities over time, and acidic water will further accelerate this process.
Substrate made of rounded glass spheres looks original, can be illuminated from below, and is completely safe for fish. However, it is completely useless in terms of biological filtration. It requires constant cleaning, as even a small amount of waste spoils its appearance. Bright multicolored and glass pebbles distract attention and prevent one from fully appreciating the natural beauty of fish and plant coloration.
When setting up a pseudo-reef aquarium, you can use the same materials as for a marine tank. For instance, natural marble chips or synthetic dyed substrates can be used as bottom material. There are no restrictions on substrate grain size since there will be no live plants in this setup. Not too fine white marble chips, sprinkled in places with beige or gray substrate, look the most natural. Despite the aquarium being bright and contrasting, the use of unnatural artificial substrate colors such as blue, green, and red is not recommended.
Tall pots or containers protruding above the substrate should be surrounded by stones so they do not spoil the overall natural look of the aquarium. This same method should be used in tanks housing substrate-digging Cichlidae. Among other benefits, potted culture has the advantage that during bottom cleaning, the pots can simply be lifted out of the aquarium and replaced afterward without damaging the roots.
Substrate in small round aquariums, which so desperately need biological filtration, should be no thicker than 1 cm; otherwise, uneaten food particles will accumulate abundantly, leading to rotting and water quality degradation. There is only one correct piece of advice here: choose a single maintenance technology out of the many available for planted aquariums and follow it scrupulously. If you want a high-tech Amano-style aquarium with intensive fertilization and extreme lighting — do it. If you want a traditional tropical forest aquarium with natural substrate silting and slow development — do it. But do not mix these and other unspecified technologies. Do not apply traditional aquarium methods to a high-tech setup and vice versa.
Purchased substrate always contains some amount of debris — clay, silt, fine sand. Before placing the substrate into the aquarium, it must be prepared. Start with thorough washing. The substrate must be washed until the draining water becomes completely clean and free of turbidity. If this is not done thoroughly enough, a suspension will remain in the water for several days that even filters cannot handle. Afterward, it is recommended to heat-treat (bake) the substrate on a baking sheet. Baking destroys any organics accidentally preserved in the substrate, and therefore microorganisms that could cause fish diseases.
When using organic-rich substrate taken from a natural water body where fish live, there is a risk of infecting aquarium fish with diseases or parasites. Therefore, it is best not to use substrate from such bodies of water, or if used, it must undergo complete treatment involving washing and baking. Pond substrate is best avoided in aquariums.
For plants that require soft water, the substrate must be freed from calcium and magnesium salts. This is achieved by washing the substrate with a 30% sulfuric acid solution. Sand and gravel are treated in an enamel container, stirring with a wooden stick until gas bubbling stops. Afterward, the substrate is rinsed under running water for 2 hours; no other disinfection is required. Caution must be exercised when using acids. After chemical treatment of the substrate, acidifying the water is not necessary.
Next, let’s examine which substrate types are suitable for the roots of various plants. There are three broad groups of aquatic plants classified by root type. The first group consists of plants that do not need substrate because they attach their roots to rocks and driftwood; this group includes Anubias, Microsorum, and Bolbitis. The next group includes plants with large storage rhizomes, such as Aponogeton and Nymphaea, as well as all stem plants like Hygrophila and Rotala, which have fine roots. The final group comprises plants with well-developed root systems, such as Cryptocoryne and Echinodorus.
Each group requires an appropriate substrate. If the substrate layer is not deep enough, for example, for the last group of plants, roots will intertwine, and plants that derive their primary nutrition through roots will suffocate. Echinodorus tenellus and Echinodorus grisebachii, both possessing long root runners, require a substrate layer of at least 6 cm. When an aquarium contains all three types of root systems, which is frequently the case, you must provide a substrate suitable for the plants with the largest root system. Fertilizers should be added only to the bottom layer so they leach into the water slowly, helping you avoid algae blooms.
In any aquarium substrate, more or less pronounced aerobic and anaerobic zones will exist. Their proportions will depend on the particle size making up the substrate and its degree of pollution. The root system of most plants will prefer the boundary between these zones, as it represents the richest (in diversity) layer containing nutrients from both zones, with these nutrients existing in unstable forms capable of easily transitioning from one state to another (oxidized, partially oxidized, and reduced forms). A moderate degree of substrate fouling corresponds best to this situation.
Pay attention to the leaves of the plants. Their normal position (this mainly applies to plants relying primarily on root feeding) is close to a 45-degree angle relative to the substrate surface. This leaf arrangement is most convenient for collecting settling detritus and directing it toward the root rosette. Plants in substrates ranging from poor to moderately fouled are characterized by this leaf posture.
In an aquarium, the space for root development is limited and hermetically isolated on all sides. Unless special measures are taken, groundwater remains stagnant, unlike natural biotopes where plant roots are constantly washed by groundwater both horizontally and vertically. To counter this, it is necessary, first, to replicate natural horizontal and vertical water movements in the substrate to ensure an even distribution of nutrients and removal of plant excretions. This slows down substrate aging and, more importantly, prevents souring. Not only nutrients but also oxygen, which plant roots need during the light period, enters the substrate.
This is achieved either by aerators (air pumps) or filtration units. Both air pumps and filters in an underwater garden must run continuously 24/7. If undergravel filtration ( plenum / false bottom) is used, the ideal particle size should be 4–5 mm. This size provides a large surface area for bacterial colonization while preventing the gravel from clogging too easily. Alternatively, a layer of coarse gravel can be placed at the bottom, topped with fine gravel. These two layers should be separated by a special plastic mesh available at pet stores.
After passing a certain abstract point of optimal substrate conditions (externally seen as peak plant growth), the aging process begins. This involves a gradual increase in anaerobic zones within the substrate, and plants react accordingly. Cryptocoryne, for example, position their leaves parallel to the substrate, bend their petioles in an arc along their entire length, and curl the leaf blade edges downward. They try everything possible to prevent detritus from collecting at the root rosette. They are no longer able to process the amount of nutrients accumulated in the substrate and water.
Substrate heating. Good results can be achieved using heating cables. A heating cable is a long cable laid directly above the glass bottom of the aquarium beneath the substrate. The effect of their application lies not only, and perhaps not as much, in heating as in creating water currents within the substrate (rising warm currents over the cable and falling cold currents between cables), which prevents substrate souring. Very little heat is required to form these necessary convective water currents, so heating cables are usually low-power, and although left on 24/7, they imperceptibly raise the aquarium water temperature.
Slow convective currents carry small amounts of oxygen through the substrate, keeping it from souring. If you decide to use a heating cable, you should plan for it in advance, as installing it in an established planted aquarium is extremely difficult. The cable is laid out on the aquarium bottom and covered with 5 cm of substrate. Cables are available in both 220V versions and low-voltage transformer-powered versions. The latter is safer in case of cable damage but significantly more expensive. In general, according to safety regulations when working in an aquarium, all electrical equipment should be unplugged.
Substrate additives for plant nutrition. Clays.
Substrate for plants made of sand, gravel, and pebbles. 
