Substrate

So many options, so many options

What are my choices

There are three common substrate methods of thought. I will try to cover all three of them here and let you decide which one is best for you.

No substrate at all

• With this option the hobbyist leaves the bottom of the tank exposed. I believe the method of thinking is that with no substrate to collect detruis then the nitrate levels in the tank will be lower. Also maintenance  is easy since you just siphon anything you can off the bottom.

Crushed Coral (CC)

• In my option a crushed coral (CC) substrate is more visually appealing than the above option. Using CC as a substrate has its advantages. One of the advantages is that if your PH and Calcium levels drop lower than they should be the CC has the ability to leach calcium out into the water giving you a small boost. A CC substrate also looks somewhat natural since its composed of ground up shells and coral skeletons.
• Disadvantages of CC include the following. Depending on the depth of your CC substrate there is the potential that it could trap detruis causing unnecessary high nitrate counts. A CC substrate can be siphoned with the use of a gravel vacuum. All of the books I have read have suggested a CC depth of 1/2 to 1" at a maximum. The second big disadvantage to CC is that it contains sharp edges and large particle sizes. These sharp edges and shapes provide a hazardous environment for all the little "critters" that live in the substrate.

Sand bed

• Shallow Sand Bed (SSB)
• A Shallow Sand Bed (SSB) is a sand bed that is less than 3" in depth. Many hobbyist go with a SSB because it looks even more natural when compared to the two options above. A sand bed also provides a safe habitat for all of those "critters" that live in a healthy substrate. The only disadvantage that I know if with a SSB is that unlike a CC substrate you can NOT vacuum or siphon it. If you tried to siphon a sand bed you would effectively pull the sand out with the water because the sand particles are so small and light when compared to the CC. Due to this unless you have an abundance of sand "critters" or other clean up crew members detritus has a chance to accumulate in the SSB and that could lead to higher nitrate's.
• Deep Sand Bed (DSB)
• A Deep Sand Bed (DSB) is simply a deeper SSB. To qualify for a DSB the sand should have a depth of 3" or more (ideally 4+"). In my option a DSB is as natural a substrate as you can get. A DSB has all the advantages of a SSB but also has the advantage of being able to remove nitrate as well. In order to effectively remove nitrate there has to be a oxygen poor environment for the nitrate loving bacteria to live and thrive. This habitat is only achievable when the sand depth is greater than 3". Ideally a DSB would be 4" or more. When deciding how deep to make your DSB make sure that you happy with the looks. After all its your tank and you need to be able to enjoy it. For the very reason that you need and want a oxygen poor environment its crucial that you do not disturb the sand bed if possible. Its ok to have sand sifters but try not to stir up the sand bed by trying to siphon it or constantly rearranging the aquascape.

Different types of sand and what that means to us

Silica  based sand

• Some hobbyist confuse silica based sand as leaching silicates  into the aquarium. This is a urban legend and is false. Silica based sand is composed of rocks that have been ground down into very small particles some the size of dust and some the size of a small pebble. There is the chance that this form of sand could have hard metal deposits that could leach into the tank. While the sand of the oceans are derived from this exact process (the slow erosion of rocks from rain and weather).  The majority of the sand that can be purchased is man made sand.  Since this process occurs 1 million times faster than the natural erosion process the potential of hard metals or other sediments could still exist in this sand.  The photo to the right shows a picture of what some silicate sand might look like (The sand that is pictured has been described to me as being "impure" silica sand.

  I personally have not tested silica sand but I have gotten the following response from someone who has.  This is what he had to say:

  "I have tested (over the years) many varieties of silica based sands. I know there are hundreds and I've only tested dozens, but all but one that I have tested leach silicate. I am NOT stating that silica somehow insidiously turns into silicate. What I am implying is that most silica based sands are impure and actually DO contain a lot of silicate. The test is easy and not really expensive. Just place the sand in RO/DI (DI is *very* important), shake, let stand for a few days, and test.
  
  The silica based sand that I found did not have any silicate was a very white sand blasting sand. I actually don't think this sand is a good fit for a sandbed because it's very "textured". In other words the individual grains are very rough and pointed. "

   

  I am guessing that the reason that the DI water is important is that RO/DI water is 99+% pure.  Water of this purity will redially absorb impurities like silicate, phosphate, nitrate, ammonia, nitrite, etc.  By using standard tap water the results may be less significant because the water is much more saturated with impurities than the RO/DI water would be.

Aragonite based sand

• Aragonite or (calcium based) sand is the optimal choice when it comes to aquarium sand. This sand has the buffering capacity of CC but also has the advantages of having of providing a much safer living condition for all the little "critters" in your substrate. Since aragonite sand is calcium based should the PH and calcium levels fall significantly below where they should be the substrate will assist in raising the calcium levels. The buffering capacity of aragonite sand should not be used as a primary method of maintaining correct calcium levels. Correct calcium levels can be maintained by frequent scheduled water changes and dosing with a good calcium additive. The photo to the right shows a picture of what some aragonite sand might look like.

You might be wondering how someone can test to see if the sand you have is silicate or calcium based.  Its quite simple actually.  Calcium has an adverse reaction when combined with standard household vinegar.  Here are some photos of a test that I performed on the two sand samples above.

A great resource for additonal information on substrates can be found on Ronald L. Shimek's website or at Candybass.com.