Here is a little article that I may finish some day and organize it correctly but I hope that it helps a little
Why change from CC to SSB or DSB?
Most of us will not use crushed coral because it is a large substrate that traps the fish waste and uneaten food that has to be vacuumed before it creates nitrates, which it will anyway. Crushed coral does not provide a very good biological zone, and many tanks are setup with CC from the get go through lack of knowledge or because it is the only substrate that an LFS sells and tells you that it is all you need, using a selling point of CC has buffering power. I have personally battled nitrates over 100 ppm during my days of CC and UGF doing frequent large water changes. So many of us have been there and had high nitrates, did a water change to lower them and they were back in a couple of days. CC has sharp edges, which is undesirable for inverts, like anemones walking around, pods or worms. No getting around it CC is high maintenance and can lead to poor water quality, frequent maintenance, sick livestock, algae blooms and more.
Sand on the other hand has more benefits. These include having far more surface area thereby making it able to handle a higher bio load of bacteria. It is less dangerous to your infauna and has a more natural look in the tank. If going with a DSB Deep Sand Bed you can have other benefits as well like finishing the denitrification or providing sand sifting, burrowing, or tunneling fish and critters a place to play. The denitrification process predominantly occurs in deeper substrates and in areas of stagnant flow where oxygen levels are depressed. And this is why deep sand beds are effective as a nitrogen export mechanism. As water slowly diffuses deeper, aerobic organisms strip all available oxygen for respiration. In the deep, oxygen-deprived layers, denitrifying anaerobes are given the opportunity to convert nitrogen compounds into nitrogenous gases, which escape via tiny bubble out of the aquarium. I believe this process can also work on a limited basis in shallow sand beds. My sand bed is no more than 2 inches deep in some spots.
So what sand do I use to build my sand bed?
The answer here is aragonite sand. Many hobbyists have found that Southdown, Yard right or its apparent new name of old castle sand works very well for reef aquariums. This is due to it being calcium carbonate based, and with an excellent grain sizes makes for a good functioning sand bed. 1/8mm is very fine> 1/256mm to 1/16mm is considered silt, and less that> 1/256mm is considered clay.
Southdown seems to mostly contains very fine to silt size particles, and maybe a few larger than 1/8mm.
Other aragonite sands are available through many LFS. If it is aragonite it is good.
The trick here is to make sure that it is aragonite and not calcite sand as many different minerals have identical chemical formulas but wildly different properties. Aragonite is orthorhombic crystal and calcite is rhobehedral, scalenohedral or prismatic crystals
This means they have a different arrangement of atoms giving them different properties of density, solubility, hardness etc. They also tend to incorporate different trace elements, based on what best fits into their different crystal structures. Aragonite will substitute larger atoms such as strontium. Calcite grabs magnesium and iron. Aragonite’s properties are much more beneficial in a closed system.
It also seems that many have used Quick Crete play sand with success though it is not calcium carbonate based, but silica based instead. No this does not mean that you will have silicates in your tank.
Very Generally speaking Silica sand, lets say industrial style is a high purity quartz (SiO2) sand. Silica is a stable compound and will not leach silicates into your tank for it has no "sillicates in it. Depending on its chemical and physical characteristics, silica sand is used as glass sand, foundry sand, abrasives ..etc. Silica sand can contain tiny amounts of impurities, such as iron, manganese, chromium, calcium, or aluminum, and give the sand its color depending on how much of these impurities are contained within. So it depends on geographically where your silica sand comes from as to how much impurities it contains. If you are going to use silica sand look for white silica sand as it is much more aesthetically pleasing
A warning about silica crystals:
Silicosis is a disabling, nonreversible and sometimes fatal lung disease caused by overexposure to respirable crystalline silica. More than one million U.S. workers are exposed to crystalline silica, and each year more than 250 die from silicosis. There is no cure for the disease, but it is 100 percent preventable if employers, workers, and health professionals work together to reduce exposures.
So in other words do not breath this dust. FYI there is also a warning label required by the state of California that is required on silica play sand.
Ways to test sand to see if you might be able to use it in your aquarium:
Take a sample of your sand and test some of the sand with vinegar. If it bubbles/dissolves, it is calcium carbonate sand and should be safe to use.
Take some sand and pass a magnet over it or in it, it might come out with little metal shavings from processing, if it does I would not use it. Though I have heard of some who have with little poor effects. Iron can actually be a fertilizer for macro algae.
What steps should I take to change my Crushed coral to a Sand Bed?
This is project that can take some time and effort, I therefore believe that one of the safest methods is to find temporary homes for any fish and corals until you have completed the change.
You will need one or more containers like Rubbermaid bins to house your fish and one for your live rock and corals, this will also mean having enough heaters (if in the north) and power heads to keep things warm and circulating. I would also recommend saving much of the water from the existing tank without disturbing the crushed coral substrate yet. You will also need to make some fresh saltwater as if you were doing a water change which in essence you will be.
If using dry sand:
So here we go – Step 1: Remove any existing rocks, corals, fish, and other inverts to their temporary homes using the existing water from the tank, and save much of the water left if possible. Make sure that any existing filter material containing your bacteria bed be kept wet and circulating if possible, this will help prevent severe spikes from the change, or at least keep them to a minimum.
Step 2. Remove the crushed coral. This can be a mess depending on how your CC was maintained; there could be plenty of evil waste and fouled water here. Now here if you wish or need to you can save some of this CC to seed your sand bed by placing it in nylons and making some CC nylon balls 6 or 8 should be plenty.
Step 3. With the tank empty its time to do a complete cleaning of the inside of the tank, scrape off that old algae, check the silicone seems for any problems.
Step 4. My preference here is to place a layer of egg crate down on the bottom of the tank making sure that it is still an inch or two away from the sides of the glass. This way the egg crate will help to prevent any reefalanche that may happen. Some will build a PVC stand to place the rocks on so that the sand bed will not cover several inches of expensive live rock. Others will use cheap base rock and place the live rock on top of that.
Step 5. With the egg crate, PVC stands, or bare bottom tank in place. Place a layer of sand down, about 1 inch. Then start to aquasacpe using your rocks that you will place on the bottom of the sand bed, twist the rock in a little to help stabilize it. Then pour the rest of the sand in.
Step 6. Slowly add your water, the speed at which you do this may depend on if you have some corals in the first pieces of live rock that you placed in your tank, but for the most part the slower the better, this may help to reduce cloudiness.
Options include using all dry sand, all live sand, mix of both. If you can get your hands on the Southdown then that is what I would use.
Thomas
