Aquarium sand – what types of sand are there?

Aquarium sand is a popular substrate for the aquarium. In the last blog post we already clarified whether sand or gravel should be used for the aquarium. Today we want to give you more information about aquarium sand.

What is aquarium sand?

If you are just about to set up your aquarium, you will probably stand in front of the shelf at the retailer and discover that there are also aquarium gravel. Is sand not also fine gravel? That is true, of course. But the term sand is used when the gravel is finer than 2 mm. But don’t stick too closely to the term, but rather to the grain size. Because some manufacturers seem not to have understood this 😉

  • Aquarium sand < 2 mm grain size
  • Aquarium gravel > 2 mm grain size

The most common grain sizes for sand

Both the gravel and sand always have a grain tolerance. This means that a range of a grain size is specified. Below you will find the most common grains in the trade, ranging from very fine, fine to coarse:

  • 0.1-0.3 mm
  • 0.1-0.4 mm
  • 0.2-0.6 mm
  • 0.4-0.8 mm
  • 0.4-1.4 mm
]Of course there are also other exotic sizes. As we described in the last blog post, some animal species need certain grain sizes. Mussels and snails, for example, which like to dig in, like to have a particularly fine grain size. Shrimps like the sand to be a little coarser grained. They work with the small grains and look for their food here

The sand colour

The colour of aquarium sand is a question of taste. Fish and plants will cope with all colours. But the better you imitate the natural environment of an animal species, the more comfortable it will feel. Nature has not given animals certain colours for nothing. So the colour is supposed to camouflage some animals and make others particularly visible.

I personally am a friend of white and beige, because I can observe the animals especially well here. In my tanks I mix different grain sizes and colours in certain areas. It is interesting to observe that different species of animals like to stay in different places. But in the end everybody has to decide for himself which colour he chooses.

Carefully you can classify the colours of certain regions (there are differences here too):

  • Amazon red, brown to black
  • Africa light grey to white
]By the way, bright colours are particularly effective on particularly dark floors

Why do you need aquarium sand?

The aquarium floor is the solid base of the biotope in your aquarium. It has several functions:

  • Storage and release of nutrients
  • Protection for animals
  • Support for plants
  • Hostel for useful bacteria that break down pollutants
  • important for the food intake of some animal species
  • Living space for aquarium inhabitants
  • Hygiene agent for fish
  • Fish hatchery
]The aquarium floor not only gives the plants support and the possibility to develop their roots, but also stores the required nutrients and releases them to the plants when needed. Mussels and snails, for example, bury themselves in the sand to filter the water and absorb their food. The sand is not only their natural habitat, but also offers protection from predators

But bacteria also settle in the aquarium sand and break down negative pollutants such as heavy metals. Many fish, crabs, shrimps and other animals rummage the ground for food. The bottoms are also a kind of "hygiene agent" for some fish. So they can use them to flush and clean their gills. This can be observed particularly impressively in butterfly cichlids:


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It is important that you actually use aquarium sand. This should be as little harmful substances as possible and not be sharp-edged. Playing sand or building site sand has sharp edges, your fish can injure themselves on it. You can see this quickly if the animals constantly rub against plants and furniture. Another reason is that sand for outdoor use is often mixed with fungicides. This kills plants and animals in a very short time. So it is worthwhile to invest money in a reasonable substrate.

Calculate amount of sand for the aquarium

I am often asked how many bags of aquarium sand are needed for the aquarium. It depends on how much you want to have here. The more height you provide the tank with, the better the roots can take root and the animals can develop. But you will also have more pleasure in setting up the tank with more ground. If you want to fix stones, sticks or roots, this is much easier to do with a thicker layer of aquarium sand. With the rule of thumb 5-12 cm you can do this very well. The bigger the tank is, the higher the layer should be.

Now we have clarified the filling level, but we still need a formula to calculate it. The formula calculates how many kg of sand are needed.

Formula volume aquarium

Let's first calculate how much sand will fit into your aquarium if you fill it to the desired height - that is, the volume of sand.

Bottom height (5-12cm) x aquarium length x aquarium depth / 1000 = sand volume in litres

Now we only have to find out one kilo number, for this we multiply the litre value by 1.6 kg.

Sand volume L x 1.6 Kg = amount of aquarium sand in kilograms

If your sand is particularly fine, then a little more may be needed. If you want to work with gravel, then exchange the 1.6 for the 1.5 kg.

Aquarium sand gets mouldy - what to do?

Aquarium sand has the advantage that most creatures in the underwater world feel particularly comfortable with it. But compared to gravel, it also bears the danger of starting to rot. There are various methods that can be used prophylactically to prevent a rotting spot:

  • Regularly vacuum the sand surface with the mulch vacuum
  • Not too much feeding, so that as little food residue as possible remains on the ground
  • Break up substrate
  • Colonize animals that fly through the ground (example: trumpet snails)
  • Choose animals that clean the floor (example: catfish, suckers, crabs and shrimps)
]If you have received this information too late and there are already rotting spots in the sand, then you have to assess the extent of the damage. If there are smaller areas, you can suck them out with a hose. If a particularly large area or many places are affected, then you should replace the sand completely. If the rotten spots are not removed, they will increase and put a strain on the water quality. This has an effect on the well-being and health of the residents

Where does the mould in the aquarium come from?

Plants give off parts and roots rot. Food remains on the bottom and fish excrete excrement. These are the most common reasons why sand begins to rot.

Conclusion on aquarium sand

As a final word, one can say that sand is easier to maintain because it is easier to clean. It imitates the habitat of most animal species and plants particularly well. Many animal species, such as some species of catfish or mussels, depend on it as a substrate. It looks very beautiful and has many advantages. I can recommend it to both beginners and professionals.

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