All about the planted tank substrate

The benefit of maintaining natural plants in the aquarium is one of the usual questions among newcomers. The answer is obvious, natural plants contribute to the stability of our facility by consuming directly or indirectly many of the waste compounds that are created in the aquarium. Natural plants, as we have already mentioned in other sections of this section, need micro and macronutrients to develop. These compounds are assimilated from those present in the water column where a strong presence of oxygen is observed and in the substrate where we find a poor presentation of this gas. This article we will dedicate to the substrate that would become the foundations of the planted aquarium and we will see the importance of your choice and a good disposition of it prior to the implementation of our installation.

The substrate plays an important role both in the development of the plants and in the biological balance of the system. The colonies of bacteria responsible for the transformation of nitrite into nitrate and the latter into harmless nitrogen gas are installed on it and in different strata. The presence of one or the other in the different strata is due to the amount of oxygen present. Oxygen-rich surface layers are populated by nitrite-transforming nitrifying bacteria. While in the lower layers of anaerobic or oxygen-poor environments the bacteria responsible for the transformation of nitrate are installed. In addition these bacteria are also responsible for the reduction of nutrients transforming them into compounds assimilable by plants.

The planted tank substrate is an important part of the appearance of the aquarium; in fact they come in different colors to help you create a spectacular frame for your fish or your plants. However, you should also bear in mind that the substrate you choose will be the surface where the populations of beneficial bacteria settle to keep the water free of nitrogenous waste inside the aquarium. It also serves to “camouflage” the waste of fish and food remains until the time of cleaning.

Before installing any type of planted tank substrate it is important to wash it with plenty of water to remove dirt or very fine particles that could be suspended in the aquarium water and turn it cloudy. In the case of aquariums with many plants, special substrates must be used or fertilizers added. In marine aquariums it is recommended not to use stones or sand that come from the earth, as they may contain minerals or other contaminants that alter the quality of the water. When you select the substrate you should take into account three main factors: color, particle size and reaction with water.


The range of substrates for plants is as broad as plant species with specific needs. A bet to guarantee to each plant the levels of fertility, drainage and, even, what is the effect that soil will have on a certain vegetable species.

To know this last aspect, it is important to pay attention to some initials that we will find in each planted tank substrate bag: An indicative of the percentages of Nitrogen (N), Phosphorus (P) and Potassium (K) in a given composition. Thanks to him, we can know exactly what nutrients we will be contributing to a plant to achieve either flowering (for this, the substrate will have a high rate of Phosphorus and Potassium), or only the growth and maintenance of the green color of indoor plants (in this case, the percentage that will be the priority of Nitrogen).

Universal substrate: suitable for most plants. It is characterized for being a spongy, porous earth (thanks to the presence of perlite in its composition), with a balanced pH (between 6.5 and 7) and easy hydration. In addition, it keeps irrigation water well. It is an ideal substrate for both indoor plants and outdoor plants, and even for the garden.

The gravel or grit is the substrate for aquariums more popular. Generally it is inert, that is to say that it does not exchange molecules with water and the pebbles are quite soft, without sharp edges or tips that can hurt the fish. The ideal size is 3-4 mm. Which allows the passage of water for a biological filtering by the bacteria that are installed as the aquarium matures. The larger pebbles allow water to pass through but offer a smaller surface area for bacteria to settle. If you want to install a filter under the substrate, you will have to use gravel and not sand. To choose the color keep in mind that one with pebbles of different shades will better hide the dirt produced by the fish than a completely white or light colored one.

Another type of planted tank substrate is sand for aquariums. This has particles the size of sugar grains, which do not leave enough space for water to circulate or for bacteria to settle. To minimize this effect it is recommended to place a layer that is not very thick. Another problem that occurs is when you want to siphon the bottom of the aquarium to remove the dirt, because the small particles are absorbed and lost with water. This substratum is useful if you have fish in the background, because it is very soft and does not hurt their mouths and appendages while they dig for their food. It is also recommended if you have species of fish or invertebrates that dig to hide or sea cucumbers, which ingest substrate to extract nutrients.

If you are going to install a saltwater aquarium with coral you can choose gravel for corals, conchilla or aragonite. These are composed of calcium carbonate, which dissolves slowly in water and thus help keep the pH stable and slightly alkaline in the aquarium. These types of substrate are served in various shades and sizes, so you can choose the one you like most for your decoration. The verdict is that the planted tank substrate must be carefully chosen!