A Deep Sand Bed for your saltwater aquarium is one of The Most Effective Filtration Methods you can have. A deep sand bed is probably one of the most common additions to live rock filtration utilized within the marine aquarium.
What best determines the saltwater tank’s sand bed filtration capabilities is the sand particle size and the depth of the sand bed.
It’s beneficial to utilize sand particles in a deep sand bed which are normally below 0.2mm but above 0.05mm. The smaller the sand particle the better. Never use crushed coral as a sand bed. Crushed coral will trap uneaten fish food and fish waste. This waste will rot in your water, causing all kinds of issues for your saltwater fish and coral.
This is one of the best sand brands for adding a sand bed to your saltwater aquarium. A majority of saltwater aquarium sand beds run between 1″-2″ deep.
No matter what type of substrate (sand) you use in your saltwater aquarium, there will be organisms which will make this their home. A great many of these beneficial organisms are what keep your saltwater aquarium thriving.
The granular size of 0.05mm to 0.2mm being so small allows the various organisms to be able to move around the sand as they wish without being hindered in any way, therefore they are able to consume detritus (fish waste) contained within the sand as long as there are enough organisms actually present.
The sand bed, regardless of depth, must get ‘turned over’. What this means is that while the creatures who call the sand bed their home are busy burrowing around looking for food to eat the sand is actually being moved around due to their burrowing activities. Turning over a sand bed is very important, as it stops any dead areas from forming. Another important aspect of turning over a sand bed is that saltwater can penetrate very slowly through the sand bed, fostering further bacterial colonization.
Live sand is sand which is full of the valuable life which all saltwater aquariums need. It goes without saying that LIVE SAND is also deep within the oceans. Live sand can be used in a deep sand bed as long as the particle size is correct.
When a sand bed starts to get deeper than 2+ inches, then anaerobic areas will start to form. Anaerobic areas in a sand bed are areas which are very low in oxygen content, this is because the oxygen is being used by the aerobic bacteria above. Water flow through these lower areas occurs partly because of the burrowing activities of the organisms which live in the sand, but is primarily due to an activity called diffusion. All fluids have a tendency to perform diffusion. Diffusion is basically where two amounts of the same fluid which contain a different amount of chemicals balance themselves out over time via utilizing the movement of molecules.
It is these anaerobic areas which allow for denitrifying bacteria to function and convert nitrate into nitrogen gas, which will escape the aquarium at the water surface.
So an effective deep sand bed has the ability, because of grain size, depth and various organisms, to permit both nitrifying and denitrifying bacteria to co-exist and continuously break down matter all the way through to the conversion of nitrate to nitrogen gas.
When a deep sand bed is combined with live rock in the marine aquarium, any solid waste which settles upon the sand is broken down via the deep sand bed and the rest is cycled via the live rock’s excellent filtration capabilities – a match made in heaven.
Leaving live rock out of the equation though when a deep sand bed matures the following will happen:
- Waste is broken down when it lands upon the surface of the bed either via bacterial processing or via organism consumption.
- The upper layer is so oxygen rich that ammonia and nitrite is converted into nitrate.
- At the same time the nitrate concentration is being converted into nitrogen gas the nitrate created in the upper layers is ‘pulled’ down into the lower layers of the sand bed.
- When the nitrate reaches the lower levels it is converted into nitrogen gas.
- The nitrogen gas which is created rises through the sand and diffuses into the water column before being released into the air at the water surface.
- The cycle continues.
A deep sand bed has a never ending biological filtration cycle which is complete all the way through to the conversion of nitrate to nitrogen gas. The majority of other filtration methods such as water changes or tank filters help to filter the saltwater tank.
In a deep sand bed nitrate levels can be kept so low that even professional water test kits can struggle to achieve a reading (provided that other aquarium management techniques are adequate). This is very beneficial to a saltwater tank when maintaining the lives sensitive creatures, from fish to coral to microscopic organisms in the water.
Another benefit of a deep sand bed (3 or more inches) is the continuous release of planktonic larvae. These come from the reproductive activities of the organisms within the sand bed. Along with the very low nitrate levels which can be achieved there could also be a continuous supply of fresh food which is beneficial if you are keeping corals which require feeding. For this reason it is important that if the sand bed is not located in the display aquarium but in a sump, it is placed after the skimmer otherwise this fresh food could be skimmed out of the water.
It is recommended you do not add more than 1 inch of sand depth per month to an existing saltwater aquarium sand bed. The reason for this is that you need to give the organisms (which already exist in your existing sand) time to move upwards in the sand. If you add, say, 4 inches of sand at one time, then the organisms would not have had the chance to climb to safety before their oxygen ran out.
A better way is to actually remove any existing sand from the system and start with a fresh sand bed.
Building a sand bed from scratch rather than upgrading really is a simple task to undertake. All you do is purchase the sand of the correct granular size, clean it and put it into your aquarium around the live rock up to the required depth. Once you have added the sand you will need to seed the sand bed with some organisms.
With the introduction of the above and the eventual migration of creatures from the live rock into the sand all you have to do is let good old mother nature get to work.
If you are adding sand into an established tank then you will probably experience a small dust storm. This can easily be removed via mechanical filtration and any dust which has settled on either the corals or live rock can easily be blown off.
Lets go over a few tips.
- Small size sand grains below 0.2mm and above 0.05mm must be used. Using sand of the correct size will allow the substrate to be turned over.
- Some heavier material (Small live rock no larger than 1cm) may need to be placed on top of the sand if you have a high flow aquarium otherwise the sand will literally blow away and you will have a water based sand storm to deal with.
- The depth should be greater than 3 inches to create the required anaerobic areas which are essential for the conversion of nitrate to nitrogen gas. The average depth in the majority of aquariums is between 4 and 6 inches as no benefit has been seen in sand beds greater in depth than this.
- Diversity and population will decide if a deep sand bed will filter effectively. The sand bed should be alive with various types of life (copepods, amphipods, brittle stars, bristle worms etc). There are literally hundreds of different species which dwell in and around sand beds serving similar and different roles. The higher the population of organisms the better the sand bed will be able to filter which makes us happy as aquarists.
- Increase diversity whenever possible – we do not wish one or two species to become dominant.
- Avoid fish and other animals which feed upon life in and on the sand bed as in no time at all the life forms could be decimated. This includes sand sifting star fish.
Passive sand sifters are a good idea as they help to keep the upper levels clear as well as promoting the re-growth of bacteria in these areas. I recommend that you keep the addition of these sand sifters low as they may remove the food source from getting to other organisms in the sand bed.
- Feed the organisms in the sand bed. Feeding increases both diversity and the population. A deep sand bed can deal with a large amount of food. When I say food I do not mean placing fish food etc on the sand bed I mean the food in the water, however feeding frozen fish food to the sand bed is good when you first start the bed as it increases the population. Do not just give the sand bed clean filtered, skimmed water ensure that it does get water which is dirty – i.e. un-filtered and un-skimmed.
A deep sand bed combined with a live rock filtration system is one of the best natural filtration methods currently available to the marine / saltwater aquarium.
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