The deep sand bed (DSB) is a popular filtration addition used by many aquarists. Also, interest is added to the aquarium – the DSB over the course of time should develop its own population of life.
Using live rock for bio-filtration is popular nowadays. Linking the live rock with a DSB gives a really good filtration base and the overall environment of the aquarium should be improved.
The question is, where should the DSB be placed? The first and obvious choice is the display aquarium because the sand will also provide a decorative effect. Is this the best choice though?
The DSB is at least 4″ (circa 10 cm) deep, so at the front viewing plate this depth of sand will show. This may not bother the aquarist, and if it does it is a simple matter to place a decorative strip across the bottom of the front glass. So that isn’t a problem.
One problem often arises because of the construction of the DSB. This is from very fine sand, so fine it can drift easily. It is very important for the health of livestock that the seawater has sufficient movement. These currents could easily blow the fine sand and spoil the sand bed. Much like sand affected by waves on the shore, the sand could pile up in some areas. It could even leave a bare aquarium bottom in others. This is obviously not desirable as the sand may rise above the decorative strip placed to hide it, and worse the DSB will not properly function. The fine sand could also accumulate on rockwork which would spoil the décor.
A DSB in the display aquarium could have another disadvantage. Rockwork is always placed on the aquarium bottom, or raised above it on a plastic support, not on the sand. This avoids instability and avoids sand compression. The DSB is pushed around the rock base and at first could look decorative and natural. It is a potential area for accumulation of detritus as seawater flow may well be reduced low down in the aquarium, particular around some bottom areas of the rockwork. This detritus needs to be removed with minimal disturbance to the sand, a task that is not particularly easy with fine sand present.
Livestock such as fish are usually present in an aquarium, the exception being the coral only reef. Fish are constantly looking for food and the tiny life that should appear in and on the DSB will be subject to predation. This sounds fine as live food is good for fish. However, in such a small area this sand dwelling life may not survive the predation. Some will survive in the live rock, but sand dwelling life is important to the health of the DSB.
So if having a DSB in the display aquarium is not the best course of action, what is? Many, perhaps most aquarists have a sump. This may have equipment in it and be used solely for this and the extra seawater gallonage it provides. If this is the case then a DSB could go in.
The aquarist will still require the sump to house equipment and this can be arranged. Fixing a glass or marine safe plastic plate into the sump to keep sand away from the return pump is straight forward, even with an operating system. If heaters are present they can be positioned above the DSB, and if a protein skimmer is present the intake can be the same.
The guideline for the minimum surface area of a DSB is 2/3rds the base area of the display aquarium – this is not always achievable, so the largest area that is should be used. The sump probably presents the largest area as the whole of the base, excluding the return pump area, is available. It depends on the size of the sump used of course. In the display aquarium the area between the rocks and the aquarium glass is available, and then not often down the back.
There will not be a problem with fine sand blowing about – the guideline for the flow rate through the sump is 3 times the total system gallonage per hour. The DSB can be placed into position more easily and the depth can be uniform. There will not be a problem with unwanted detritus and if anything does accumulate it can be more easily removed.
The life forms that inhabit the DSB will be protected from predation, though there will probably still be predation from other tiny sand living life. The DSB life is more likely to maintain its presence and population.
There is another way that a DSB could be introduced and that is to include an area above the sump to include it. This is done by placing a shallow (5 or 6″ high (circa 12.5 to 15 cm)) glass container above the sump, level with one end but stopping where the pump area in the sump begins. The down feed for the seawater from the aquarium is diverted to the DSB at one end; it then overflows at the other into the sump, being returned to the display aquarium as usual. It doesn’t take a lot of imagination to find alternatives to the same theme. This method keeps the sump area clear for other uses, and doesn’t add much seawater to the system (though adding more gallonage is not a bad thing).
Some aquarists run their display aquariums bare-bottomed, though the bare bottom doesn’t usually last long as various marine growths take over. Others employ a decorative sand bed 1″ to 2″ deep (circa 2.5 to 5 cm), this one made of coarse sand, though this too could be blown by seawater currents. The advantages of having a decorative sand bed are that there aren’t any filtration requirements so changes to the bed don’t matter, and they are easier to clean by stirring if dirt appears.
As said, keeping a DSB is a good move in aquarium husbandry. For practical reasons, it is better housed away from the display aquarium.