The substrate in the aquarium fulfills several functions. On the one hand, gravel, sand or soil naturally looks beautiful in the aquarium - much nicer than a glass bottom on which more and more mulm and food remains slowly collect. With a dark aquarium bottom, shrimp and fish look much more intensely colored, and many aquarium animals have much less stress on dark substrate than on light substrate. However, there are also aquariums in which a light substrate can be used, quite a lot also depends on the personal taste of the keeper of the aquarium. On the other hand, the substrate in the aquarium acts as a gigantic filter and offers the useful aquarium bacteria an almost infinitely large area on which they can settle and clean the aquarium water from pollutants. In addition, of course, the substrate in the aquarium is still an important factor for the aquarium plants, which eventually want to root somewhere.
The basic difference between active Soil and gravel is that active Soil affects the water values and makes the water soft and slightly acidic. Active Soil basically performs the function of an ion exchanger in the aquarium, thereby lowering the carbonate hardness. Humic substances in the Soil stabilize the pH value at a value of about 6.5 - ideal for the vast majority of aquarium plants and also for very many aquarium animals that come from biotopes with soft water.
With the Soil there is strongly pre-fertilized Soil for plant aquariums, which must be run in first of all over two weeks without animal occupation. During this time, the Soil releases a lot of ammonium into the aquarium water, which is why you should change water regularly during the run-in phase of a Soilaquarium. Soil for shrimp, on the other hand, is not pre-fertilized and can be stocked more quickly. The ammonium spikes are not as high or not present at all.
Because the small grains of Soil are formed from dark natural soils, which are then baked at low temperatures, Aquarium Soil is, with very few exceptions, dark brown to almost black. Soil for aquariums is not washed out - the grains are not very stable and would simply crumble to mud when washed out. However, because Soil is always stored in a moist place, it does not generate dust.
Gravel or sand, on the other hand, are basically either water-neutral or slightly harden the aquarium water. If it doesn't say whether the gravel or sand is hardening, you can easily check - put some sand in a small glass and pour vinegar essence over it. If it starts to bubble, the substrate contains lime and may be hardening the aquarium water.
Aquarium gravel and aquarium sand come in various natural colors - light, dark, brown, reddish, beige, variegated ... - and in different grain sizes from very fine to very coarse. With different grain sizes you can design the bottom in the aquarium just as great as with different gravel colors or sand colors.
Colorful gravel is also possible for the aquarium. However, it is absolutely important that the gravel is dyed with food coloring and coated with synthetic resin. Anything else can release pollutants into the aquarium water and should therefore not be used, especially for bottom-dwelling aquarium animals such as shrimp, crayfish or catfish. However, colored gravel coated with synthetic resin and food coloring for the aquarium is harmless. Even if color particles should come loose during heavy abrasion, these are not harmful to the stock.