This is a very good question which I was asked recently via email and I thought that I would detail it here for others to read and hopefully benefit from.
A lot of aquarists decide to put a small amount of decorative sand in the bottom of the aquarium to make it look more natural. This sand is normally something like coral sand, live sand etc.
Normally a small scattering is put in the aquarium – just enough to cover the bottom of the aquarium. At first the aquarium does look very natural however before long the sand starts to get clogged up with detritus, uneaten food and unless the aquarist cleans it then it can start to look very dirty.
Whilst looking into possible methods to keep it clean the aquarist may stumble upon a term called deep sand beds. After a small amount of research the aquarist may decide to ‘give it a go’ and after purchasing more of the sand installs it into the aquarium and believes that he/she now has a deep sand bed.
Wrong I am afraid and this is a deep sand bed which is probably destined to fail.
The reason for this is that the sand used in a deep sand bed has to have sand particles which are within a given size range. This is so that the animals which live in the sand are able to move the sand around. This is a term which is called turning the sand bed over. The animals will not magically appear. Some will migrate from the live rock if this is used in the aquarium, however the majority will need to be introduced by the aquarist. Not just once either the bed will need to be topped up from time to time. Once the bed has animals in there they then need feeding so that they can reproduce and increase the diversity in the sand bed. For this they need to be fed by placing some food directly onto the sand bed alternating where the food is placed. Other animals can also be purchased and introduced to the aquarium to assist in the cleaning up of the sand bed. These can be hermits, starfish etc but they have to be ones which will survive in a sand bed.
The other thing that is required is the actual depth of the sand bed. The sand bed needs to be a minimum of four inches in depth. Having a deep sand bed of at least this depth will create a bed which is low in oxygen at the bottom. When this happens this allows for the relevant bacteria to live which will assist in the filtration.
There are a large amount of aquarium stores now that sell sand which is designed for use in the the creation of a deep sand bed. There is a variety of colours to choose from however personally I prefer the natural ‘sand’ looking colour!
A deep sand bed is a very powerful tool for filtration and is often underestimated. Combine a deep sand bed with live rock and you have an aquarium filtration system with a large amount of power. As long as it is properly setup and properly cared for.
In answer to the question – yes decorative sand can be used for filtration as long as the fundamentals of deep sand beds are understood.
Below are links to two articles we recently wrote on this subject: