Lets Talk Substrates for the Marine Aquarium

[JimG1966]

Nice write up and very informative. I thought you would end up with a hydrogen sulfide gas bubble no matter what you did and have been preached to not to pop the bubble. Had I known if i had just went alittle deeper with the sand this would be an issue I would not have to worry about I would have added a couple more bags. I vacuumed the sand in our 125 and was told I cleaned the tank to good and caused a few issues since I popped the bubble. Now every time i go to do anything my wife is standing there freaking out about me popping it again. Pretty sure if I try to add more sand to a 8 month old tank it will cause it to cycle again if I understand all that I have read. I will keep all of this in mind when setting up the 210. Since its going to house stingrays I had already planned on putting a pretty deep sand bed in it.

 

[JimG1966]

The "live" sand generally doesn't recommend rinsing - but it can still be mighty cloudy for a few days. There are plenty of folks who feel that the touted benefits of live sand are negated by the siltiness of it. I used live sand without rinsing to start my tanks, and also committed what might be considered the "cardinal sin of sand" by transferring 80 pounds or so from an existing tank. (That sand, however, was rinsed thoroughly!) Rinsing can be done in a bucket, with a hose, a few pounds at a time, until the water runs clear. It's a chore, for sure!

~Bruce

if you rinse your sand with a hose and bucket doesnt that kill the live sand since your putting it in fresh water with chlorine?

 

[bGGN088]

Thanks for the article, as new to the saltwater hobby, I think i might try a layer of CC or CS with a thin layer of sand. So, that over time my cleaning of the substrate will mix the the two better.

 

[Jay Norris]

Hi, just finished with a complete overhaul of my sand bed. I removed about 98% of the old sand, which had been in the tank for 10 or so years, and replaced with new sand collected off the Outer Reefs of the Florida Keys, took a little over a month to complete the process, and everything seems to be doing just fine, as it's been about 10 days since I added the last Live Reef Sand.

 

[anon9896]

I own a pistol shrimp, so I would never consider possible my water to be 100% sand particles free . I would love to debate the benefits and the harms caused by such particles in the water column. I notice myself keeping corals that needs more frequent feedings than most reefers. Maybe is it becose of the sand itself and or becose the shrimp keeps mixing it around ‍. It sure does a superb job to keep it clean.

 

[tim132]

Lets Talk Substrates for the Marine Aquarium

Bare-bottom (BB)? Calcium Carbonate (CC) Gravel? Crushed Shell? Sand? Deep vs. Shallow? With all the choices that are out there, no wonder new hobbyists are often confused about which substrate to use for their marine aquarium. In this thread, I shall attempt to address pros and cons of each of the available substrates.

Please remember however, that the choice of substrate must be balanced with two things; Aesthetic value to the viewer and biological value to the livestock. Some fish and inverts require a certain type or depth of substrate, and proper research should be done to ensure that the hobbyist is correctly matching the substrate with the needs of the aquarium's livestock. Sand-sifting gobies such as the Diamond Watchmen and Yellow Shrimp gobies should never be placed in a BB or CC gravel tank, and many wrasse species require a Deep sand bed (DSB) so that they may bury themselves at night or when they perceive themselves to be in danger.

Bare-Bottom (BB): Bare-bottom refers to an aquarium that has no substrate at all. The bottom remains clear, and allows the hobbyist to easily clean up any left over food or debris which may be floating around, using a net, siphon, or state of the art filtering system. This lack of substrate is preferred by those hobbyists who prefer a clean, sterile look in their aquarium, and is often recommended for a quarantine tank. While maintenance is easy, it must be done regularly as debris blowing around the tank can be very unattractive. The lack of substrate means that the hobbyist is gaining no natural filtering benefit from the substrate and is unable to keep sand-dwelling inverts or sand-sifting fish. Additionally, Extra care must be taken when building rock structures or when working in a BB tank as there is nothing to absorb the impact should a rock wall collapse. And finally, refugium lights on a reverse cycle can shine up through the glass bottom, causing the aquarium to be lit from below; therefore individuals may wish to consider painting their bottom.


A study conducted on the denitrifying effects of sand beds noted what appeared to be a correlation between substrate depth and aquarium deaths; with death rates up to twice as high in shallow substrate tanks, and a word of caution that "it doesn't get much shallower than bare-bottom." While I've attached a link to the article, I urge caution in reading too much into the study, as this was not the focus of the actual research.

Feature Article: An Experimental Comparison of Sand bed and Plenum-Based Systems: Part 2: Live Animal Experiments — Advanced Aquarist's Online Magazine

Calcium Carbonate or Dolomite Gravel (CC): Commonly referred to simply as CC, calcium carbonate gravel used to be the most common substrate in marine aquariums, but has since fallen out of favor among hobbyists, although it is still used by some. Larger particles (usually 5 to 20mm in size) of calcium carbonate or dolomite are placed in a layer from 1/4" to 1 1/2" deep over the bottom of the aquarium. The primary reason for its fall from favor is that many believe that CC acts as a trap for uneaten food and debris and turns the substrate into a nitrate factory. Others simply do not care for the look of CC. If the CC bed is properly maintained through regular siphoning and cleaning, it is no more of a nitrate factor than any other substrate. Calcium carbonate and dolomite are both hard substances that break down slowly over time releasing calcium carbonate into the water, helping to maintain calcium levels and buffer pH in the marine aquarium. Calcium carbonate is the same substance from which many marine inverts, such as snails and many species of coral build their skeleton. Dolomite, although similar in appearance to CC is less soluble and breaks down slower as a result.

(Photo courtesy of Paul Baldassano)​

Crushed Shell (CS): Another substrate that has found some small amount of favor among hobbyists is crushed shell. Typically composed of the shells of assorted types of shellfish, CS is generally smaller than the particle size of CC and is generally more aesthetically pleasing to hobbyists, especially those who are familiar with shell-covered beaches. Like CC the CS breaks down, releasing calcium carbonate into the water, however, because it is not as hard as CC or dolomite, it breaks down and dissolves much faster. Additionally, the fine shell pieces in the uppermost layer quickly color up with coralline algae, just as the shells of snails and hermit crabs in your aquarium do. Like the CC if not properly maintained through regular siphoning, the crushed shell can become a nitrate factory as debris and fish waste break down.


Sand: Generally the favored substrate of today's modern reef aquariums, many feel that sand gives the marine aquarium a much more natural look. Additionally, the sand bed provides a place for the growth of micro-fauna and bacteria which aid in the biological filtering of the marine aquarium. Sand is used to cover the bottom of the aquarium to various depths and now is available in a variety of colors (from pink to black), size (very fine "sugar sand" to large grains) and name brands. It is generally recommended to use aragonite sand, so that it, like the CC can bread down slowly over time adding calcium carbonate to the water and helping to buffer pH. Silicate-based sand (usually referred to as play sand) should be avoided; it compacts readily, creating a concrete-like substrate and releases silicates into the water which can cause diatom blooms. Properly setting up any sand bed requires the introduction of bacteria and micro-fauna through the introduction of true Live Sand (not the bagged stuff purchased off the shelves from your LFS which at best contains only bacteria). Some of the disadvantages of a sand bed include sandstorms in the event of too strong of a current within the aquarium and sand being dropped onto LPS polyps. A sand bed is required to properly maintain certain species of fish and invertebrates, however care should be taken in the selection of livestock for the marine aquarium with a sand bed. Some critters, such as Diamond Watchmen gobies and sand-sifting sea stars, can quickly consume all the micro-fauna and bacteria in the sand bed in a smaller tank, thus causing the sand bed to become inert and no longer function for biological filtration. Once they have consumed all the micro-fauna, these animals will often slowly starve.

​

Shallow vs. Deep Sand beds: Generally speaking, 1/4" to 2" is considered to be a shallow sand bed (SSB) and 3 1/2" to 6" is considered a deep sand bed (DSB). Generally the area between the two is considered to be an unsafe zone, not quite deep enough for anaerobic bacteria to establish and carry out denitrification, but too deep for aerobic bacteria to be present, thus allowing the build-up of toxic wastes in the form of hydrogen sulfide gas which can be released if the sand bed is disturbed.
(Your photo of a shallow sand bed aquarium here)

It has generally been accepted that SSB, like CC, maintain oxygenated water throughout the sand bed and therefore must be maintained by siphoning, generally on a monthly basis. While DSBs on the other hand have an anaerobic area (typically in the bottom inch or two) very similar to Live Rock, in which anaerobic bacteria are able to establish to help break down nitrates. The DSB requires little to no regular maintenance (some do regularly siphon or stir the top inch or so). Recent research however indicates that both shallow and deep sand beds function in converting organic waste into free nitrogen gas. I've attached a link to the two articles that report these finding below.

Feature Article: An Experimental Comparison of Sand bed and Plenum-Based Systems. Part 1: Controlled lab dosing experiments — Advanced Aquarist's Online Magazine

Feature Article: An Experimental Comparison of Sandbed and Plenum-Based Systems: Part 2: Live Animal Experiments — Advanced Aquarist's Online Magazine

Alternative Materials: A growing number of individuals have also began experimenting with a number of different alternative materials in place of going bare-bottom. Starboard or Corian is one of the more popular alternatives. These materials have similar benefits to BB tank, in that they are easy to siphon off detritus and wastes, and one never has to worry about stirring up sandstorms or clearing sand from LPS polyps. They have the additional advantages of having something in place to absorb a heavy impact in the event of the collapse of rock work, and they lack the sterile look of a BB tank. The lack of substrate however, again means the hobbyist is gaining no natural filtering benefit from the substrate, and is unable to keep any sand-dwelling inverts or sand-sifting fish. Additionally, as with the BB, regular maintenance is required, as accumulated debris blowing around on the bottom can be unattractive, as can the board itself. Further as with the BB, refugium lights on a reverse cycle can shine through from the bottom, so consideration should be given to painting the bottom of the tank.

Thanks very much. I was literally just asking a question about substrate!

 

[Gup]

Lets Talk Substrates for the Marine Aquarium

Bare-bottom (BB)? Calcium Carbonate (CC) Gravel? Crushed Shell? Sand? Deep vs. Shallow? With all the choices that are out there, no wonder new hobbyists are often confused about which substrate to use for their marine aquarium. In this thread, I shall attempt to address pros and cons of each of the available substrates.

Please remember however, that the choice of substrate must be balanced with two things; Aesthetic value to the viewer and biological value to the livestock. Some fish and inverts require a certain type or depth of substrate, and proper research should be done to ensure that the hobbyist is correctly matching the substrate with the needs of the aquarium's livestock. Sand-sifting gobies such as the Diamond Watchmen and Yellow Shrimp gobies should never be placed in a BB or CC gravel tank, and many wrasse species require a Deep sand bed (DSB) so that they may bury themselves at night or when they perceive themselves to be in danger.

Bare-Bottom (BB): Bare-bottom refers to an aquarium that has no substrate at all. The bottom remains clear, and allows the hobbyist to easily clean up any left over food or debris which may be floating around, using a net, siphon, or state of the art filtering system. This lack of substrate is preferred by those hobbyists who prefer a clean, sterile look in their aquarium, and is often recommended for a quarantine tank. While maintenance is easy, it must be done regularly as debris blowing around the tank can be very unattractive. The lack of substrate means that the hobbyist is gaining no natural filtering benefit from the substrate and is unable to keep sand-dwelling inverts or sand-sifting fish. Additionally, Extra care must be taken when building rock structures or when working in a BB tank as there is nothing to absorb the impact should a rock wall collapse. And finally, refugium lights on a reverse cycle can shine up through the glass bottom, causing the aquarium to be lit from below; therefore individuals may wish to consider painting their bottom.


A study conducted on the denitrifying effects of sand beds noted what appeared to be a correlation between substrate depth and aquarium deaths; with death rates up to twice as high in shallow substrate tanks, and a word of caution that "it doesn't get much shallower than bare-bottom." While I've attached a link to the article, I urge caution in reading too much into the study, as this was not the focus of the actual research.

Feature Article: An Experimental Comparison of Sand bed and Plenum-Based Systems: Part 2: Live Animal Experiments — Advanced Aquarist's Online Magazine

Calcium Carbonate or Dolomite Gravel (CC): Commonly referred to simply as CC, calcium carbonate gravel used to be the most common substrate in marine aquariums, but has since fallen out of favor among hobbyists, although it is still used by some. Larger particles (usually 5 to 20mm in size) of calcium carbonate or dolomite are placed in a layer from 1/4" to 1 1/2" deep over the bottom of the aquarium. The primary reason for its fall from favor is that many believe that CC acts as a trap for uneaten food and debris and turns the substrate into a nitrate factory. Others simply do not care for the look of CC. If the CC bed is properly maintained through regular siphoning and cleaning, it is no more of a nitrate factor than any other substrate. Calcium carbonate and dolomite are both hard substances that break down slowly over time releasing calcium carbonate into the water, helping to maintain calcium levels and buffer pH in the marine aquarium. Calcium carbonate is the same substance from which many marine inverts, such as snails and many species of coral build their skeleton. Dolomite, although similar in appearance to CC is less soluble and breaks down slower as a result.

(Photo courtesy of Paul Baldassano)​

Crushed Shell (CS): Another substrate that has found some small amount of favor among hobbyists is crushed shell. Typically composed of the shells of assorted types of shellfish, CS is generally smaller than the particle size of CC and is generally more aesthetically pleasing to hobbyists, especially those who are familiar with shell-covered beaches. Like CC the CS breaks down, releasing calcium carbonate into the water, however, because it is not as hard as CC or dolomite, it breaks down and dissolves much faster. Additionally, the fine shell pieces in the uppermost layer quickly color up with coralline algae, just as the shells of snails and hermit crabs in your aquarium do. Like the CC if not properly maintained through regular siphoning, the crushed shell can become a nitrate factory as debris and fish waste break down.


Sand: Generally the favored substrate of today's modern reef aquariums, many feel that sand gives the marine aquarium a much more natural look. Additionally, the sand bed provides a place for the growth of micro-fauna and bacteria which aid in the biological filtering of the marine aquarium. Sand is used to cover the bottom of the aquarium to various depths and now is available in a variety of colors (from pink to black), size (very fine "sugar sand" to large grains) and name brands. It is generally recommended to use aragonite sand, so that it, like the CC can bread down slowly over time adding calcium carbonate to the water and helping to buffer pH. Silicate-based sand (usually referred to as play sand) should be avoided; it compacts readily, creating a concrete-like substrate and releases silicates into the water which can cause diatom blooms. Properly setting up any sand bed requires the introduction of bacteria and micro-fauna through the introduction of true Live Sand (not the bagged stuff purchased off the shelves from your LFS which at best contains only bacteria). Some of the disadvantages of a sand bed include sandstorms in the event of too strong of a current within the aquarium and sand being dropped onto LPS polyps. A sand bed is required to properly maintain certain species of fish and invertebrates, however care should be taken in the selection of livestock for the marine aquarium with a sand bed. Some critters, such as Diamond Watchmen gobies and sand-sifting sea stars, can quickly consume all the micro-fauna and bacteria in the sand bed in a smaller tank, thus causing the sand bed to become inert and no longer function for biological filtration. Once they have consumed all the micro-fauna, these animals will often slowly starve.

​

Shallow vs. Deep Sand beds: Generally speaking, 1/4" to 2" is considered to be a shallow sand bed (SSB) and 3 1/2" to 6" is considered a deep sand bed (DSB). Generally the area between the two is considered to be an unsafe zone, not quite deep enough for anaerobic bacteria to establish and carry out denitrification, but too deep for aerobic bacteria to be present, thus allowing the build-up of toxic wastes in the form of hydrogen sulfide gas which can be released if the sand bed is disturbed.
(Your photo of a shallow sand bed aquarium here)

It has generally been accepted that SSB, like CC, maintain oxygenated water throughout the sand bed and therefore must be maintained by siphoning, generally on a monthly basis. While DSBs on the other hand have an anaerobic area (typically in the bottom inch or two) very similar to Live Rock, in which anaerobic bacteria are able to establish to help break down nitrates. The DSB requires little to no regular maintenance (some do regularly siphon or stir the top inch or so). Recent research however indicates that both shallow and deep sand beds function in converting organic waste into free nitrogen gas. I've attached a link to the two articles that report these finding below.

Feature Article: An Experimental Comparison of Sand bed and Plenum-Based Systems. Part 1: Controlled lab dosing experiments — Advanced Aquarist's Online Magazine

Feature Article: An Experimental Comparison of Sandbed and Plenum-Based Systems: Part 2: Live Animal Experiments — Advanced Aquarist's Online Magazine

Alternative Materials: A growing number of individuals have also began experimenting with a number of different alternative materials in place of going bare-bottom. Starboard or Corian is one of the more popular alternatives. These materials have similar benefits to BB tank, in that they are easy to siphon off detritus and wastes, and one never has to worry about stirring up sandstorms or clearing sand from LPS polyps. They have the additional advantages of having something in place to absorb a heavy impact in the event of the collapse of rock work, and they lack the sterile look of a BB tank. The lack of substrate however, again means the hobbyist is gaining no natural filtering benefit from the substrate, and is unable to keep any sand-dwelling inverts or sand-sifting fish. Additionally, as with the BB, regular maintenance is required, as accumulated debris blowing around on the bottom can be unattractive, as can the board itself. Further as with the BB, refugium lights on a reverse cycle can shine through from the bottom, so consideration should be given to painting the bottom of the tank.

Hello i just started my salt tank its a 45 an i added my live sand it was clear this morning cloudy all day yesterday. i decided "hey its clear why not even out the sand" now its cloudy again lol is this the tank just needing to settle? should i leave my two flow pumps/wave makers on?

 

[Gup]

Got my nickname in the 6th grade, 70 yrs now and still called GUP.

I had a SWFO 55gal tank some 40+ years ago. An undergrave filter / dolomite. Damsels, dragonet, Dwarf Hawaii Lion, Copperband Butterfly & 6 Seahorses. How things have changed & NOT surprisingly. I'm back in business again.

I just completed a 55 gal high, along with a 15 gal +/- 6 chamber sump. Built my REEF with 50lbs of Marco Rock... Rubble/stone /shelves. It's 3 columns, 7 passages. It's 27in wide x 17in high x 7in deep. Substrate is 40lbs of dry Aragonite & I just topped that off with a 10lbs bag of live Carib. I'm in the diatom stage now, I'll be happy when the purple Coralline takes hold. I added 2 juvenile yellow-belly damsels and 1 baby Clown yesterday.

 

[Tbg299]

I went with a Fiji pink SSB (1"). It is the most natural looking reef sand to me. I rarely have to gravel clean my sand bed because my goby does most of the work.

 

[Vincentete]

great article! thanks!
i have been using sand, but always wanted to try crushed coral at some point.

 

[Gigaboom]

I'm getting a smaller mantis shrimp species and have a sand bed that varies from about 1 1/2" to 3" in some places, but most of it is 2" to 2 1/2". is this in the unsafe zone and if so, should I add more sand or remove some sand?

 

[brandon429]

This article on reef substrate is completely outdated and should not be a sticky reference. since it is, we need to address that nobody can tell you where a good or a bad zone is in reefing substrates, that kind of control and prediction is completely made up by typers online.

substrates vary..99% don't have dangerous zones anywhere in the stratified layers of a common sandbed, and any animals that kick up waste via boring holes in the sand or jawing the sand like a diamond goby are just kicking up waste clouds to cast around the tank but it doesnt crash systems.

1% of systems have waste so badly compacted, any disturbance of the sand that is new and not part of prior procedure kicks up really bad waste from any zone in the bed and that can cause big invasion outbreaks and in small cases depending on the degree of upwelling systems can crash out due to poisons in the stored waste we've yet to define.

you can use that mantis however you like in the current bed, adding or - sand won't matter, you likely have no bad zones at all. if you wanted to be the safest we can be, you'd have a sandbed that is cleaned regularly vs allowed to store up waste, that's the safest condition possible no matter which sand you use. messing with dirty sandbeds is the risk

being able to design a marine sandbed that uptakes and reduces nitrate vs produces it like a dirty diaper is also made up by forum typers, nobody has that type of control. for 25 years we've been told all deep sandbeds reduce nitrate, and now we can see in hindsight that's not true for 99.999% of sandbed owners.

 

[PaPaWicked85]

This has helped me decide what substrate I'll go with. Going to try DSB first, and go from there. Seeing some really good results in multiple places online from it. Thanks for this post!

 

[BettytheDancer]

This is a wonderful article. Do we have something like this for filtration?

 

[Trizz]

I'm about to do a bare bottom.

 

[Oldguy]

Lets Talk Substrates for the Marine Aquarium

Bare-bottom (BB)? Calcium Carbonate (CC) Gravel? Crushed Shell? Sand? Deep vs. Shallow? With all the choices that are out there, no wonder new hobbyists are often confused about which substrate to use for their marine aquarium. In this thread, I shall attempt to address pros and cons of each of the available substrates.

Please remember however, that the choice of substrate must be balanced with two things; Aesthetic value to the viewer and biological value to the livestock. Some fish and inverts require a certain type or depth of substrate, and proper research should be done to ensure that the hobbyist is correctly matching the substrate with the needs of the aquarium's livestock. Sand-sifting gobies such as the Diamond Watchmen and Yellow Shrimp gobies should never be placed in a BB or CC gravel tank, and many wrasse species require a Deep sand bed (DSB) so that they may bury themselves at night or when they perceive themselves to be in danger.

Bare-Bottom (BB): Bare-bottom refers to an aquarium that has no substrate at all. The bottom remains clear, and allows the hobbyist to easily clean up any left over food or debris which may be floating around, using a net, siphon, or state of the art filtering system. This lack of substrate is preferred by those hobbyists who prefer a clean, sterile look in their aquarium, and is often recommended for a quarantine tank. While maintenance is easy, it must be done regularly as debris blowing around the tank can be very unattractive. The lack of substrate means that the hobbyist is gaining no natural filtering benefit from the substrate and is unable to keep sand-dwelling inverts or sand-sifting fish. Additionally, Extra care must be taken when building rock structures or when working in a BB tank as there is nothing to absorb the impact should a rock wall collapse. And finally, refugium lights on a reverse cycle can shine up through the glass bottom, causing the aquarium to be lit from below; therefore individuals may wish to consider painting their bottom.


A study conducted on the denitrifying effects of sand beds noted what appeared to be a correlation between substrate depth and aquarium deaths; with death rates up to twice as high in shallow substrate tanks, and a word of caution that "it doesn't get much shallower than bare-bottom." While I've attached a link to the article, I urge caution in reading too much into the study, as this was not the focus of the actual research.

Feature Article: An Experimental Comparison of Sand bed and Plenum-Based Systems: Part 2: Live Animal Experiments — Advanced Aquarist's Online Magazine

Calcium Carbonate or Dolomite Gravel (CC): Commonly referred to simply as CC, calcium carbonate gravel used to be the most common substrate in marine aquariums, but has since fallen out of favor among hobbyists, although it is still used by some. Larger particles (usually 5 to 20mm in size) of calcium carbonate or dolomite are placed in a layer from 1/4" to 1 1/2" deep over the bottom of the aquarium. The primary reason for its fall from favor is that many believe that CC acts as a trap for uneaten food and debris and turns the substrate into a nitrate factory. Others simply do not care for the look of CC. If the CC bed is properly maintained through regular siphoning and cleaning, it is no more of a nitrate factor than any other substrate. Calcium carbonate and dolomite are both hard substances that break down slowly over time releasing calcium carbonate into the water, helping to maintain calcium levels and buffer pH in the marine aquarium. Calcium carbonate is the same substance from which many marine inverts, such as snails and many species of coral build their skeleton. Dolomite, although similar in appearance to CC is less soluble and breaks down slower as a result.

(Photo courtesy of Paul Baldassano)​

Crushed Shell (CS): Another substrate that has found some small amount of favor among hobbyists is crushed shell. Typically composed of the shells of assorted types of shellfish, CS is generally smaller than the particle size of CC and is generally more aesthetically pleasing to hobbyists, especially those who are familiar with shell-covered beaches. Like CC the CS breaks down, releasing calcium carbonate into the water, however, because it is not as hard as CC or dolomite, it breaks down and dissolves much faster. Additionally, the fine shell pieces in the uppermost layer quickly color up with coralline algae, just as the shells of snails and hermit crabs in your aquarium do. Like the CC if not properly maintained through regular siphoning, the crushed shell can become a nitrate factory as debris and fish waste break down.


Sand: Generally the favored substrate of today's modern reef aquariums, many feel that sand gives the marine aquarium a much more natural look. Additionally, the sand bed provides a place for the growth of micro-fauna and bacteria which aid in the biological filtering of the marine aquarium. Sand is used to cover the bottom of the aquarium to various depths and now is available in a variety of colors (from pink to black), size (very fine "sugar sand" to large grains) and name brands. It is generally recommended to use aragonite sand, so that it, like the CC can bread down slowly over time adding calcium carbonate to the water and helping to buffer pH. Silicate-based sand (usually referred to as play sand) should be avoided; it compacts readily, creating a concrete-like substrate and releases silicates into the water which can cause diatom blooms. Properly setting up any sand bed requires the introduction of bacteria and micro-fauna through the introduction of true Live Sand (not the bagged stuff purchased off the shelves from your LFS which at best contains only bacteria). Some of the disadvantages of a sand bed include sandstorms in the event of too strong of a current within the aquarium and sand being dropped onto LPS polyps. A sand bed is required to properly maintain certain species of fish and invertebrates, however care should be taken in the selection of livestock for the marine aquarium with a sand bed. Some critters, such as Diamond Watchmen gobies and sand-sifting sea stars, can quickly consume all the micro-fauna and bacteria in the sand bed in a smaller tank, thus causing the sand bed to become inert and no longer function for biological filtration. Once they have consumed all the micro-fauna, these animals will often slowly starve.

​

Shallow vs. Deep Sand beds: Generally speaking, 1/4" to 2" is considered to be a shallow sand bed (SSB) and 3 1/2" to 6" is considered a deep sand bed (DSB). Generally the area between the two is considered to be an unsafe zone, not quite deep enough for anaerobic bacteria to establish and carry out denitrification, but too deep for aerobic bacteria to be present, thus allowing the build-up of toxic wastes in the form of hydrogen sulfide gas which can be released if the sand bed is disturbed.
(Your photo of a shallow sand bed aquarium here)

It has generally been accepted that SSB, like CC, maintain oxygenated water throughout the sand bed and therefore must be maintained by siphoning, generally on a monthly basis. While DSBs on the other hand have an anaerobic area (typically in the bottom inch or two) very similar to Live Rock, in which anaerobic bacteria are able to establish to help break down nitrates. The DSB requires little to no regular maintenance (some do regularly siphon or stir the top inch or so). Recent research however indicates that both shallow and deep sand beds function in converting organic waste into free nitrogen gas. I've attached a link to the two articles that report these finding below.

Feature Article: An Experimental Comparison of Sand bed and Plenum-Based Systems. Part 1: Controlled lab dosing experiments — Advanced Aquarist's Online Magazine

Feature Article: An Experimental Comparison of Sandbed and Plenum-Based Systems: Part 2: Live Animal Experiments — Advanced Aquarist's Online Magazine

Alternative Materials: A growing number of individuals have also began experimenting with a number of different alternative materials in place of going bare-bottom. Starboard or Corian is one of the more popular alternatives. These materials have similar benefits to BB tank, in that they are easy to siphon off detritus and wastes, and one never has to worry about stirring up sandstorms or clearing sand from LPS polyps. They have the additional advantages of having something in place to absorb a heavy impact in the event of the collapse of rock work, and they lack the sterile look of a BB tank. The lack of substrate however, again means the hobbyist is gaining no natural filtering benefit from the substrate, and is unable to keep any sand-dwelling inverts or sand-sifting fish. Additionally, as with the BB, regular maintenance is required, as accumulated debris blowing around on the bottom can be unattractive, as can the board itself. Further as with the BB, refugium lights on a reverse cycle can shine through from the bottom, so consideration should be given to painting the bottom of the tank.

So where to aquire "true live sand" as opposed to the LFS "bagged stuff"...??

 

[Tripod1404]

Thanks for the article, as new to the saltwater hobby, I think i might try a layer of CC or CS with a thin layer of sand. So, that over time my cleaning of the substrate will mix the the two better.

My tank is a 50:50 mix of CS and fine sand. Keep in mind that smaller size particles will sink to the bottom over time and you will end up with larger stuff on the top.

Surface of my substrate is not mostly CS with few pockets of sand created by excavating fish that actively bring it to the top. My sand shifting goby than spreads it around the tank.

One benefit of CS, it turns into a massive pod factory since there are relatively large pockets where pods and algae can thrive.

 

[Joseph_Joe]

For my tank I used 2 kinds of sand :
- Lower layer is silicate based.
- Upper layer is carbonate based.

I wanted to have 2 types of sand in order to gain chemical & biological benefits from the both type. However, I also get the drawbacks, e.g. the silicate sand is leading to regular diatoms blooms, and the carbonate based is sometimes difficult for the CUC to burry below it.