Living space in the aquarium.
Knowledge about the natural living space of fish will help the aquarist avoid major mistakes in their maintenance. Most fish like an aquarium divided into many areas and corners. Since the living space of the tank is enclosed, and weaker fish cannot escape in the struggle for dominance, they must be given the opportunity to hide behind some barrier or shelter. Every fish can get used to certain deviations thanks to its ability to adapt. However, it is necessary to be extremely attentive to all details of the aquarium setup and technical devices, especially when dealing with fish known for their pickiness.
The environment inside the aquarium (its interior design) should be considered from two perspectives: from the observer’s point of view and from the perspective of necessity (usefulness) for the inhabitants. The first perspective is pointless to discuss: “there is no accounting for tastes.” Here is the only recommendation: your imagination should not go so far as to harm the fish. But what suits the fish?
For all living things on Earth, there are practically only two “commandments”: preservation of one’s own life and reproduction of offspring, and the first is only needed to fulfill the second. Indoor aquarium design must provide conditions for the preservation of life and reproduction. Further, everything is quite simple: nutrition, respiration, shelter. The first has nothing to do with design. The second is only relevant regarding good ventilation of the lower water layers. The third condition is provided by this principle: a fish behaves more boldly if it knows that at the first sign of danger there is somewhere to hide.
It is good when an aquarium with cichlids has large driftwood and stones, while at the same time leaving enough space for free swimming. Almost universally, Cichlidae are fish that build their nests for breeding in the form of pits in secluded places of the aquarium. Therefore, the bottom of the aquarium should be covered with at least a five-centimeter layer of fine river gravel with individual fragments 3-6 mm in size.
Elements of decorating a tropical aquarium can be a few large stones, well-boiled picturesque driftwood, or tree branches. When choosing driftwood and branches, preference should be given to old and strong ones that have been underwater for a long time. Stones, rosette plants, and overgrown driftwood form the central part of the composition in the aquarium, while the background and sides are traditionally planted with long-stemmed plants. The bottom area occupied by greenery should not exceed 40-50%, meaning there is no need to fear open areas.
The substrate should be rounded, fine (fractions up to 5-7 mm), containing a minimum of calcareous inclusions. Usually, planted aquariums use a substrate layer from 3 to 7 cm thick. With a smaller layer, the root system has nowhere to develop; with a larger layer, stagnant zones may form without additional tricks. The attractiveness of the landscape in the aquarium can be ensured by terracing the substrate. An interesting option is the use of two types of substrate that differ in both color shades and fraction sizes. Fine and light substrate is used to lay out bottom areas mimicking a sand spit or river shoal. Darker and larger gravel is poured around these areas for contrast. It is also good to use driftwood and stones along the dividing line.
You can make areas of bare sand by using pieces of cardboard to separate the sand from the substrate. Slowly fill both sides of the cardboard to an equal height where they touch the cardboard on both sides. Then carefully pull out the cardboard. Stones with attached mosses are also an excellent divider and support for a sloped substrate. Sandy paths and a river under a waterfall, with regular aquarium maintenance and due to animal activity, are unlikely to maintain their original appearance for long. Decorations in such aquariums are not particularly practical. In addition, a lot of free space remains around one or two objects, so the decorations do not serve as shelters for the animals. Since we are going to plant our aquarium densely, we will have to use a nutrient substrate.
Both live and artificial plants can be used to create this style. The main decoration is aquatic plants in large quantities and diverse in leaf structure, featuring a wide range of rosette and hard-leaved plants. An aquarium decorated with live plants requires a more thoughtful selection of fish, as the needs of the plants must also be taken into account. A combination of artificial and live plants is also possible. When choosing plants, you need to understand that many of them in nature grow at a depth of no more than 30 cm or even in damp soil occasionally flooded with water. Accordingly, you will not be able to grow everything in a deep aquarium. Small plants are planted in groups, like islands; large ones are placed separately, closer to the back wall. Free swimming spaces for fish are left in the front.
A fish accustomed to living over a sandy bottom must find it in the aquarium as well. Thus, fish of the genus Geophagus like to dig up the bottom with their heads in search of food. Of course, fine gravel will also suit them, but on the other hand, they can pass sand through their gills, whereas small grains of gravel cannot. Consequently, you can help fish through a thoughtful aquarium setup or, conversely, make their existence and food search difficult if the aquarium is decorated incorrectly. Be prepared to abandon any idea if it, while pleasing to the eye, may lead to physical or psychological discomfort for the aquarium’s inhabitants.
Logic suggests that the number of fish and plants should be limited by the volume of water in the tank. Water is of decisive importance! The number of aquarium inhabitants is calculated based on the number of liters, not the capacity of the tank. In this case, the volume of bottom substrate and stones should be subtracted. Most often, mistakes of this kind are made immediately, already at the time of purchasing fish. Amateurs do not take into account (by the way, this also applies to plants) that they are dealing with young, immature specimens — such fish, with good care, will multiply their initial size many times over after some time.
The aquarist needs to remember these conditions and sometimes refuse to buy new fish to guarantee the established “population” of their aquarium the necessary living space. The species and quantitative composition of fish in your aquarium may depend on many factors: the size of the aquarium, the size of the fish themselves, as well as the life support system with which your home body of water will be equipped.
Setting up a traditional freshwater aquarium.
Underwater world composition. Design concept. 
