Deep Sand Bed (DSB) intro

This is an introduction to the DSB.

In my opinion the important points of this method are:

Set-up costs are reduced, as the quantity of live rocks is reduced by more than 50% and the technique (in particular lighting and skimmer) for the same tank size are less expensive.
– The aquarium set up with DSB acquires a very natural and extremely bright appearance.
– It is possible to breed invertebrates and fish that without sand should not be ideal conditions.

A fundamental step is to create a sand bed about 12/15 cm high (minimum 10 cm if using particularly fine sand and maximum 15 if using a coarser grain size). Usually I use a variable grain size between 600 and 1000 microns.The materials to be used for the sandy bed can be :

Aragonite sand (excellent, but very expensive),
Calcium carbonate (Cheaper)
Volcanic (in these cases, you lose the reflection of the lights that you have with the white sand)

As previously written, the height of the sand bed must be about 12/15 cm high. This in order to have the good conditions for the proliferation of different bacterial strains, ( aerobic , anaerobes, anaerobes, chemotrophs). Each of these bacterial types is necessary for the completion of the nitrogen cycle (biochemical cascade that involves the continual chemical degradation of nitrogenous from ammonia to nitrite to nitrateand) requires a different concentration of oxygen.
Using a low layer will never allow the settlement of bacteria that reduce nitrate to nitrogen gas and will only cause “incomplete digestion” of fish and invertebrate manure.

With this approach 3 layer are present:

Layer 1: Aerobic => In this layer the oxygen concentration is equal to that found above the seabed.
Layer 2: Anaerobic => In this layer the oxygen concentration is much lower.
Layer 3: Anoxic => This layer is characterized by the absence of dissolved oxygen in the water trapped in the sand

The first layer rich in transformed oxygen is the nitrification zone, where ammonium comes into nitrite; the next layer in which oxygen begins to run out, further transforms the nitrite into nitrate, while the deep layer, almost completely devoid of oxygen, is populated by chemotrophic bacteria that use the oxygen present in the nitrate as an energy source, transforming it in gaseous nitrogen which leaves the tank in the form of bubbles.

Of course the DSB needs movement and oxygenation in order to stimulate the bacterial populations characteristic of the various layers to work at maximum speed.

Maturation is term used to describe the maturing process that takes place during the first few months. The maturation lasts from six months up to a year(It is important to illuminate the tank from the beginning). Also in this method, live rocks, rich in bacteria and populated by a rich benthic fauna, necessary for the maturation and colonization of the DSB, play a fundamental role.
In any case, the setting up of the rock in the DSB leaves much more freedom, as the quantity of rocks is more than halved compared to the Berlin Method.

In the placement of live rocks is mandatory follow some simple rules:

• Cover the smallest possible surface with rocks, using “stilts” constructions if possible, making sure that the water can circulate freely and lap the sand.
• Leave as much free space as possible between the walls of the aquarium and the rock
• Leave large spaces between the rocks to avoid the accumulation of sediment and maximize oxygenation.

Once the DSB is set up, every other day it is useful to feed it with a pinch of granular feed for fish and dose a few ml of live phytoplankton.The sand must remain soft and continuously moved by benthic organisms for the DSB to perform its function as a biological filter.
The movements of benthic organisms are essential to transfer oxygen and organic nourishment between the various layers of the bottom and between the bottom and the water column.
If the benthic organisms (infauna) were not present in adequate density, crusts could form that do not allow oxygenation and the exchange of substances, leading to the collapse of the system. Therefore, given that initially there will be no benthic organisms, it is advisable to manually move the first millimeters of the DSB for the first 3-4 weeks to keep it oxygenated and prevent it from compacting.

How to calculate the amount of sand to use?

You can know it just applying the following formula:

(Tank length*Tank Width * DSB height * Sand granulometry) /1000

eg. Tank length = 100, Tank Width= 50, DSB height = 15, Sand granulometry = 15.

{100x50x15x1.3}{1000} = 97.5 Kg of sand are needed.