# Deep Sand Beds In Freshwater Tanks



## Matt69 (Jul 9, 2017)

FlatfishTanker said:


> I've watched the YouTube of Cory from Aquarium Co op when he visited the Ocean Aquarium store in San Francisco a couple times. He mentions that some of the tanks there have not had water changes for up to 25 years! At one point he directed our attention to the deep sand beds in the tanks as if maybe they had something to do with it. Can anybody here explain what's going on there? What does a deep sand bed in a freshwater planted tank do? How does it work? Does it work? Just curious if anybody has seen these videos or experienced the store and may have some insight. Thank you.
> 
> Wayne




Check out father fish on you tube, it seems he has a few video on it. 
Personally I don’t know too much about it but if I had the space and time I might try it. 


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## minorhero (Mar 28, 2019)

He talks about the sand bed for like 4 seconds heh. But its at around the 3:50 mark:






The tour itself is pretty spiffy and most of the tanks have a LOT of plant matter in them. Like 50% or more of the volume of the tank is filled with plants. This is of course how he he is getting away with few or no water changes. The sand tank is the exception because the fish in there would eat plants I believe. 

We do water changes of course to remove waste material that would build up. This includes nitrate. But if you are fortunate enough to have a colony of anaerobic denitrifing bacteria you can convert nitrate into atmospheric nitrogen which being a gas that doesn't like to be dissolved in water simply out-gasses. Pretty spiffy stuff but apparently somewhat hard to do on purpose. Or so I've been told on this forum and elsewhere /shrug. Since trying to set it up involves not doing water changes, most folk prefer to just do the water changes to guarantee fish health and happiness.


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## AbbeysDad (Apr 13, 2016)

You have to take into account that the store is selling fish and with every sale water is being removed from the tank to go in the bag with the fish...and later replaced...so this is a pseudo water change of sorts.

Live rock and deep sand beds are common in salt water. Deep sand (UNDISTURBED) creates anoxic and anaerobic areas down under where anoxic and anaerobic facultative bacteria can populate. These bacteria will extract O2 molecules from NO3 (nitrates), releasing harmless nitrogen gas. 
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This is not unlike Dr. Kevin Novak's anoxic biocenosis clarification baskets where he uses baskets of clay kitty litter to create an anoxic region. This method requires a sump or pond as the baskets are bulky and not suited for aquarium use (Although he also recommends a plenum where an under gravel filter is used but the flow is dramatically reduced to very little). I am currently experimenting with anoxic clarification baskets in a sump for my 110g stock tank...but have yet to see any noticeable nitrate reduction.
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It is also 'suggested' by some mfg's that certain bio-medias with micro pores may allow the population of these facultative bacteria to process nitrates.
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Then again.... in a heavily planted tank, where fast growing plants use ammonia as their nitrogen source (so it isn't converted to nitrates), the right stock level, proper feeding and tank/filter maintenance, only modest routine partial water changes are necessary to keep pollution at bay and fresh water fresh. ~


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## FlatfishTanker (Sep 17, 2019)

minorhero said:


> He talks about the sand bed for like 4 seconds heh. But its at around the 3:50 mark:
> 
> I know he mentions it and points it out, But he does not explain the benefit or what it does or how it works. I was hoping to learn something!


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## Blue Ridge Reef (Feb 10, 2008)

Cory doesn't go deep into water chemistry (or any subject, really). He's a passionate LFS owner who does overview videos for the beginner and intermediate hobbyist. Other posters explained pretty well what deep sand beds and the anaerobic bacteria do to consume NO3. If you want some in-depth links, I can google a few up. I'd imagine most will be reef sites, but the concept is the same.


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## FlatfishTanker (Sep 17, 2019)

Thanks Blue Ridge. I will explore and see what I can find. Thanks Matt69. Father Fish is awesome! I will spend some time with him soon and see what I can learn. When I say time, I mean you have to be patient to get to his nuggets of wisdom! I watched one video of his so far. I kept yelling at the screen, "Get to the point old man!" And he eventually did. I'm sure my patience will be rewarded.


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## Bandit1200 (Dec 11, 2010)

I'm not trying to knock you for posting the question, but it does seem a bit puzzling to me. Most of us here go through a lot of trouble to ADD nitrates to our planted tanks so I don't know why you would want to go through that much setup and potential for disaster to reduce nitrates in a planted tank.


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## AbbeysDad (Apr 13, 2016)

Bandit1200 said:


> I'm not trying to knock you for posting the question, but it does seem a bit puzzling to me. Most of us here go through a lot of trouble to ADD nitrates to our planted tanks so I don't know why you would want to go through that much setup and potential for disaster to reduce nitrates in a planted tank.


I for one am a fishkeeper first, using plants to aid in water purification and appearance. Plants prefer to use ammonia for their N2 source. Some plants will use nitrates, but must expend more energy to do so. In any case, I look to keep nitrates on the low side while still having acceptable plant growth, especially in fast growing floating plants that convert pollution into plant tissue eventually removed in trimmings.


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## FlatfishTanker (Sep 17, 2019)

Thanks AbbeysDad. I think you explained the best.


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## Desert Pupfish (May 6, 2019)

FlatfishTanker said:


> I kept yelling at the screen, "Get to the point old man!" And he eventually did. I'm sure my patience will be rewarded.


Couldn't agree more. Drives me crazy that so much info in this hobby is only available in videos. Whatever happened to writing articles that you can skim through quickly to see if it contains what you're looking for, and is worth a slow read? Watching a talking head drone on for 20 min or longer is just crazymaking to me. Guess I have no patience so won't ever be rewarded....


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## Jeffww (Aug 6, 2010)

Been to that store. Not as great close up in-person as in the videos. A very very old school store and worth visiting if you have time. Some things to learn, other things to appreciate how far modern fish-keeping has come.


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## Matt69 (Jul 9, 2017)

Jeffww said:


> Been to that store. Not as great close up in-person as in the videos. A very very old school store and worth visiting if you have time. Some things to learn, other things to appreciate how far modern fish-keeping has come.




I’m going to agree with you, there a lot of members on this forum that have tanks that look a lot better than his. 
Some of the high tech tanks on this site and other sites are getting colors that are quit amazing. 
I’m not trying to diss the old school method if that’s what you want go for it. If I had the space time and money I would think about trying one. 


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## Blue Ridge Reef (Feb 10, 2008)

Desert Pupfish said:


> Drives me crazy that so much info in this hobby is only available in videos. Whatever happened to writing articles that you can skim through quickly to see if it contains what you're looking for, and is worth a slow read? Watching a talking head drone on for 20 min or longer is just crazymaking to me.


Could not agree more. The vast majority of the time I click a link and it's a video I close it before it can even begin. Of course, this is coming from the same person who wouldn't watch Narcos Mexico last night because I didn't feel like reading subtitles.


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## Andy H (Nov 14, 2019)

> I've watched the YouTube of Cory from Aquarium Co op when he visited the Ocean Aquarium store in San Francisco a couple times. He mentions that some of the tanks there have not had water changes for up to 25 years! At one point he directed our attention to the deep sand beds in the tanks as if maybe they had something to do with it. Can anybody here explain what's going on there? What does a deep sand bed in a freshwater planted tank do? How does it work? Does it work? Just curious if anybody has seen these videos or experienced the store and may have some insight. Thank you.


*Yes I can explain what is happening in deep sand beds and why they are used in aquariums to improve water quality or just reduce the need for water changes. I can also explain and debunk myths concerning potentially toxic gasses produced by bacteria in anoxic regions of deep sand beds.* Provided you can accept the science and experience based reasoning behind why I don't worry about these gasses when using deep sand beds or substrates like dirt that restrict O2 penetration into them. At the very least I can give my practical experience with some gasses that may be produced as a result of bacteria using different electron donors preferentially in oxidation reduction reactions that produce these gasses. The release of N2 and N2O into the water will does not impact our aquariums as these gasses are out gassed leaving the aquarium completely. 

What is happening in deep sand beds is that a lack of oxygen forces bacteria in the substrate to use electron acceptors for respiration. Nitrogen is present in the environment and aquarium in a wide variety of chemical forms including organic nitrogen, ammonium (NH4+), nitrate (NO2-), nitrate (NO3-), nitrous oxide (N2O), nitric oxide (NO) or inorganic nitrogen gas (N2). The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), nitrous oxide (N2O) finally resulting in the production of dinitrogen (N2) completing the nitrogen cycle. This cycle is very important to understanding why deep sand beds are used. Denitrifying microbes require a very low oxygen concentration of less than 10%, as well as organic carbon for energy. This carbon is attainted from dead plant matter or dead bacteria. 

An electron acceptor is a chemical entity that accepts electrons transfered to it from another compound. It is and oxidizing agent that, by virture of its accepting electrons, is itself reduced in the process. 

Typically, denitrification occurs in anoxic environments, where the concentration of dissolved and freely available oxygen is depleted. In these areas, nitrate (NO3−) or nitrite (NO2−) can be used as a substitute and terminal electron acceptor instead of oxygen (O2), a more energetically favorable electron acceptor. 

Denitrification generally proceeds through some combination of the following half reactions

NO3− + 2 H+ + 2 e−→ NO2− + H2O (NO3 reduction to NO2)

NO2− + 2 H+ + e− → NO + H2O (NO2 reduction to NO)

2 NO + 2 H+ + 2 e− → N2O + H2O (NO reduction to N20)

N2O + 2 H+ + 2 e− → N2 + H2O (N20 reduction to N2)

The complete process can be expressed as a net balanced redox reaction, where nitrate (NO3) gets fully reduced to dinitrogen (N2):

2 NO3− + 10 e− + 12 H+ → N2 + 6 H2O

*Nitrification is the conversion of ammonia (NH3) to nitrate (NO2) followed by the conversion of nitrite (NO2) to nitrate (NO3) performed by aerobic bacteria. *

*Denitrification is the conversion of nitrate (NO3) to nitrogen gas (N2) by anaerobic bacteria. *

*The bacteria involved in nitrification are aerobic.

The bacteria involved in denitrification are anaerobic and facultative.*

Facultative bacteria prefer aerobic environments. They can live in aerobic or anaerobic conditions but do not participate in both nitrification and denitrification.

*The cool thing about facultative bacteria is that they can breathe through aerobic and anaerobic respiration pathways. Allowing them to use oxygen, manganese, cobalt, sulfate, sulfur, and nitrate as electron acceptors in cellular respiration. This is important to us because these electron acceptors exist in the substrate and water column as nutrients. Interestingly, facultative bacteria provide an alternative route to nitrite reduction instead of conversion to nitrate. It is worth mentioning their use of nitrate as an electron acceptor in this leads to nitrate (NO2) reduction to nitrogen gas (N2).*

*Facultative bacteria can reduce nitrite to nitrogen gas and anaerobic bacteria can reduce nitrate to nitrogen gas.* 

With this information why not use commercially available bacteria inoculants that contain all three bacteria? The only reason would be that one doesn't believe they work or they believe these bacteria already exist in their aquarium. Based on my limited experience with bacteria inoculants I have to say that they do work. Furthermore based on the frequent posts in forums needing help reducing ammonia, nitrite, and nitrate these bacteria do not magically populate our aquariums without them being introduced through inoculation or transfer from an established tank that has all three types of bacteria. You can easily attain aerobic bacteria that convert ammonia to nitrate and nitrite through this method but facultative and anaerobic bacteria are far less common because they are not given appropriate conditions, they are never introduced to the aquarium, or both. These inoculants can also be used periodically in response to high ammonia, nitrite, or nitrate levels from livestock additions or instead of water changes. 

Regarding possible hydrogen sulfide (H2S) and methane (CH4) release from anaerobic sediments and sand beds.

I believe some people confuse what happens in deep sand bed with little or no organic matter vs. what happens in natural soils composed of sediments and organic matter with a far more diverse bacterial population than present in aquariums. This is complicated by the fact that people with planted tanks using deep sand beds will have organic matter in their deep sand beds.

*In true deep sand beds hydrogen sulfide will not be produced because of the lack of sulfur in the sediment*. Furthermore, even if H2S is produced in an aquarium sediment or sand bed the hydrogen sulfide can react with oxygen to produce water and sulfur dioxide (H2S + O2 = H2O + SO2) in the aerobic layers as it moves upwards into sediment with a higher dissolved oxygen content. Hydrogen sulfide can also react with metal ions in water yielding metal sulfides which are not water soluble and will precipitate out of solution. The movement of small amounts of H2S produced in anaerobic sediments or sand beds is influenced by the grain size of the sand bed. The smaller the grain size the slower H2S will move upwards into the water column giving it adequate time to react with oxygen in the aerobic layers of the sand bed. 

*Methane is similar to hydrogen sulfide in that it is produced in sediments containing organic carbon through oxidation reduction reactions within the bacteria living in the deepest regions of soil or sediment.* The terminal electron acceptor in methanogenesis is not oxygen, but carbon. The carbon can occur in a small number of organic compounds. The two best described pathways involve the use of carbon dioxide or acetic acid as terminal electron acceptors, (CO2 + 4 H2 → CH4 + 2 H2O) and (CH3COOH → CH4 + CO2). Without access to carbon even if methanogenic bacteria are present no methane will be produced.

In my experience I prefer to employee both nitrifying and denitrifying bacteria in my aquariums. I used something similar to a deep sand bed in my last freshwater planted tank. A mixture of mineralized top soil and volcanic sand 3-4" deep. I used volcanic sand specifically because it would allow for higher bacteria densities than any other sand available do to its porosity. Even with the mixture of organic matter and anoxic regions in my substrate i lost no fish without clear explanation and never saw any signs of distressed breathing in any of my fish. I have also used deep sand beds in reef aquariums with no problems. I could actually see unknown gas bubbles moving through my substate. I assumed it was only carbon dioxide from the decomposing organic matter but it could have hydrogen sulfide. However, I never smelled the rotten egg smell associated with hydrogen sulfide.


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## Discusluv (Dec 24, 2017)

Blue Ridge Reef said:


> Could not agree more. The vast majority of the time I click a link and it's a video I close it before it can even begin. Of course, this is coming from the same person who wouldn't watch Narcos Mexico last night because I didn't feel like reading subtitles.


 As a culture we read far less than at any point where a majority of Americans were literate. This is partially due to technology, but it is also due to the high demands of work, home, family---
As a consequence, quick digestible reads that skim the surface of a topic have taken over to reflect this dynamic.


This also is reflected in the percentage of high-school graduates that get to college and are placed in remedial reading/writing courses. Quick skim reads and You-tube does a number on reading comprehension.

Bump:


Andy H said:


> *Yes I can explain what is happening in deep sand beds and why they are used in aquariums to improve water quality or just reduce the need for water changes. I can also explain and debunk myths concerning potentially toxic gasses produced by bacteria in anoxic regions of deep sand beds.* If you can accept the science and experience based reasoning behind why I don't worry about these gasses when using deep sand beds or substrates like dirt that restrict O2 penetration into them. At the very least I can give my practical experience with some gasses that may be produced as a result of bacteria using different electron donors preferentially in oxidation reduction reactions that produce these gasses including the release of N2 and N2O nitrogen gas and nitrous oxide these bacteria that will be out gassed and leave the aquarium completely.
> 
> What is happening in deep sand beds is that a lack of oxygen forces bacteria in the substrate to used different electron donors in respiration. Nitrogen is present in the environment and aquarium in a wide variety of chemical forms including organic nitrogen, ammonium (NH4+), nitrate (NO2-), nitrate (NO3-), nitrous oxide (N2O), nitric oxide (NO) or inorganic nitrogen gas (N2). The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), nitrous oxide (N2O) finally resulting in the production of dinitrogen (N2) completing the nitrogen cycle. This cycle is very important to understanding why deep sand beds are used. Denitrifying microbes require a very low oxygen concentration of less than 10% (found in properly made deep sand beds), as well as organic Carbon for energy (can come from dead plant matter or dead bacteria.
> 
> ...


 In 30 year of fish-keeping Ive never had fish die from a deep sand bed giving off hydrogen gases. 

My 180 right now ranges from 3 inches in front to 5 in back. It has a layer of ecocomplete at base, a layer of Rhizomat on top of that, and caribsea sand. Been set up for 3.5 years. 

In the past Ive used just sand, but wanted to add plants to this tank so added the ecocomplete and Rhizomat as well with this tank.


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## Backblast72 (Jul 7, 2020)

I have to admit there is some interesting information on this thread.

I just recently set up my first dirted tank. It’s a standard 75 gallon tank. My substrate is in three layers. First is 40 pounds of Echo Complete, Second is 2.5 bags of Miracle-Grow Nature’s Care organic soil which I sifted twice to remove the great majority of large debris. And the third is 60 of Quikcrete medium grade sand. The tank has been up and running since the 30th of July, so I’m in my third week of cycling my tank. I have 5 Red Melon Swords, 5 Amazon Swords, 5 Anubias Nana, 1 Anubias Congengis, Japanese Java Feen, and want to add more plants. 

Last night while eating dinner I noticed my sand bed was discolored; the sand has blotchy black spots throughout the bottom layer of the substrate, I jumped on google and everything I found was toxic build up Hydrogen Sulfide as the ‘cause for this reaction. I don’t have the smell of rotten eggs in the water. So it’s so interesting to find out that it could be the oxidation and breakdown of organic carbon compounds within the substrate due to the organic soil.

Any and all additional information regarding this matter are highly appreciated. Not a newbie to the hobby. However, this is my first dirted tank with a sand cap. So learning new and very interesting information every day.

Very Respectfully,
Carlos A. González.


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