Are Deep sand beds effective?

[jda]

Surely you do get this. People see the word "nutrient" and think that if they give their tank more N and P to "eat," that their coral use it more to their benefit. Not true. Once you have enough N and P, then you have enough. More will not help anything like more sugars can. If you are not building, then you do not need a lot of building blocks, but you do still need sugar to live.

I think that we are confusing living with growing. Sugar is needed just to maintain and live when N or P is not (as much). When you grow, you use all of these, among other things. If you add more sugars into the corals, then growth speeds up, repair speeds up. If you add more N and P, then nothing will happen faster, and might even happen slower. Carbon and hydrogen are the constraint, not the building blocks.

Bottom line - assuming that all building blocks are not below growth-limiting levels, the coral can do more with more sugar, but can not do more with more N and P.

 

[fredk]

Surely you do get this. People see the word "nutrient" and think that if they give their tank more N and P to "eat," that their coral use it more to their benefit.
...

I make no assumption about what people think when they see the word nutrient.

I just found your explanation very confusing. Corals need a constant supply of many nutrients including N and P. Too little is disastrous and its good to see that the majority are past the "zero nitrates and phosphates" phase of reefing. As N and P increase, there is an increased risk of other issues like algal blooms.

Bottom line - assuming that all building blocks are not below growth-limiting levels, the coral can do more with more sugar, but can not do more with more N and P.

This was not at all clear, at least to me, in your original post. N and P need to be available in measurable amounts, but not too high. The levels that cause problems seem to be different for every tank, but you always need some available for corals to use.

Bottom line: N and P availability (and other nutrients) are essential to good health in corals. Sugar is not some special nutrient to be elevated in importance over all other essential nutrients. Using the phrase "true nutrient" to describe sugar is very misleading.

Edit: did I forget to mention I can be a bit pedantic?

 

[427HISS]

"As an aside, I want to point out that people who uses silica sand for their sand bed have totally different experiences since phosphate binding nor buffering is possible here. Let's all just put these types of tanks off to the side since they are a whole different creature".[/QUOTE]

Hi again,
Please explain the above.

I want the added 3" of substraight for filtration, but mainly need the proper size of material for our sand sifters.
What would you advise for a 125g mixed reef with a fish load. (I will be adding a great skimmer)

 

[jda]

Silica sand does not buffer (melt if/when the pH gets low) and it does not bind/swap phosphate. People have bashed it saying that it releases silica into the water, but that does not appear to be true either. I have never used silica sand, so no real experience. I am sure that you could search for some pros and cons of using silica sand.

I just use aragonite. Mixed bed size is what I like. The last time that I ordered sand, I got like 12-15 boxes from marcorocks - I do not recommend their rocks, but the sand was clean, nice and phosphate free.

 

[427HISS]

I'll check them out. Does BRS carry the type you like ?

 

[jda]

All of the Carib Sea stuff is aragonite.

 

[427HISS]

Great. How do you like the "live" sand ?

 

[427HISS]

Great. How do you like the "live" sand ?

jda ?

 

[Belgian Anthias]

I can see you like DSB's whereas I do not, that is what is awesome about this hobby. I was not instructing the OP to use carbon dosing just to look at it as another means of nutrient export. BTW, carbon dosing works incredibly well & yes it must be used in conjunction with a skimmer...

I do not like DSB especially but I have not abounded the use bio-filters.
As a skimmer is a device which is not that effective in removing nutrients and dissolved organics ( max +- 30%) how one can say carbon dosing works "incredibly" well? Not for exporting nitrogen out of the system. So it must be incredible for other purposes!?
Carbon dosing activates the production of protein. If the produced bio-mass is not removed, it is mostly recycled, needing regular carbon dosing just to keep the cycle running.
To stay by the threat, a DSB is effective in removing nitrogen from the system.
As the removal rate can not be made controllable as would be possible when using bio-filters, the nitrate level can not be managed and maintained at the desired level.

 

[Belgian Anthias]

The above paragraph leaves me puzzled.

N and P fit into the definition of nutrients above and are no more or less essential than sugars. As pointed out in the quote above, you need essential nutrients for both repair and growth, so all organisms, including corals, always need them available for ingestion in some form or another.

All sugars are some form of carbon, oxygen and hydrogen in a specific ratio. Corals cannot get anything else from sugars. The carbon is for growth/repair. The oxygen, as far as I know, is just a nasty free radical that floats about looking for things to destructively bind to unless expelled from the coral. The hydrogen is used to generate energy at a cellular level.

Sugar is in no way some special 'true nutrient'. It has its specific purpose. Nothing more and nothing less.

Sugar is not present in natural seawater!
As the presence of organic carbon is used by nature to limit growth, that is way most of it is transformed to CO2 , it may be called a very important nutrient.

What all of this has to do with the effectiveness of a DSB!? Adding sugar to an aquarium will certainly have effect on the denitrifying capacity! But will it have a positive or negative effect?

 

[Belgian Anthias]

The amount of absorption is on a siding scale with pH, but still can be massive at any levels that we observe in a tank. I did an experiment and over 50 ppm of phosphate in 10g of water bound down to about .16 ppm with just a handful of the larger ARM calcium reactor media chunks.

The pH in the sand and inside of the rock is very stable since it is not really impacted too much by the co2 swings from photosynthesis. It is usually a bit lower than the tank. All evidence points to a stable environment where the binding happens, but I have never really seen a study that explicitly looks at this (we probably never will).

As an aside, I want to point out that people who uses silica sand for their sand bed have totally different experiences since phosphate binding nor buffering is possible here. Let's all just put these types of tanks off to the side since they are a whole different creature.

The pH in a DSB may be completely different compared to the pH in the water column. Nitrification and denitrification does change the pH in and on the sand constantly and pH may drop , depending of the substrate used. There are a lot of studies available about the effect of the used filter bed on pH, on denitrification and nitrification, the effect of produced acids in the microbial world on nitrification and denitrification and on all other processes taking place in a nitrifying biofilm. Research has been done on the effect of these processes on the dissolving rate of the used substrate.
As an example: If a nitrifying biofilm is grown on sand or any other neutral substrate it will lower the pH of the water, if grown on oyster shell grit it will not effect pH in the water column although in the filter bed more acids are produced due to the increased filtration capacity.

 

[jda]

My sand bed was around 7.4 pH when my tank pH was about 8.2. It was also around 7.4 when the tank was at 8.4 later in the day. I found it pretty immune to the daily photosynthesis-driven pH changes. However, I have not owned a pH probe in about a decade since I figured out that it just does not matter to me.

People do not understand that the two are different, which is why they think that their tank pH has to get into the 6.Xs to melt some sand and buffer a bit. It probably only needs to drop to 7.7 in the tank, with the sand getting into the 6s, or so, but each tank is different.

 

[Craig Stuart - Reefscaper]

Geeze Guys..... I'm kinda getting tired with the bad rap DSBs are getting.

I seem to be reading lots of posts about DSBs being used for nutrient reduction. Yet the term nutrient reduction is being mostly limited to only 2 parameters. Nitrate and phosphate.

Some folks describing them as nutrient traps, time bombs, people having export issues, leeching phosphate, quoting complex studies on P&N ratios etc etc.... when in all honesty just some common sense needs to be applied.

My experience has been that DSB work great for certain applications however they must be used properly and properly maintained. They are not something that can just be chucked in and left to their own devices and they do a lot more than just reduce nitrate and phosphate.

By maintained I don't mean syphoned or cleaned or refreshed with fresh sand etc etc... I mean populated with the correct fauna and flora which will assist carry out the complete removal of "nutrients" accrued in the sand over time.

A deep sand bed firstly needs to be set up properly with the correct grades of biologically active mud, sand and grades of small particle gravel. It then needs to have the correct fauna added to it and observed. Each grade or zone within a deep sand bed is a habitat in its own right for a very different group of bacteria micro or macro fauna... each having their own role to play in the break down of organic matter.

DSB are highly complex ecosystems and if not in balance will produce results which are considered unfavorable.... a car is a time bomb if not driven properly!!!

DSB placed in the display tanks have proven for me not to be suitable in SPS tanks when fish are present. Colouration of corals typically effected.

DSB are great tools for certain applications and if managed well are highly effective for nutrient reduction, process ridiculous amounts of detritus and generate large amounts of micro fauna and plankton....

 

[Belgian Anthias]

Geeze Guys..... I'm kinda getting tired with the bad rap DSBs are getting.

I seem to be reading lots of posts about DSBs being used for nutrient reduction. Yet the term nutrient reduction is being mostly limited to only 2 parameters. Nitrate and phosphate.

Some folks describing them as nutrient traps, time bombs, people having export issues, leeching phosphate, quoting complex studies on P&N ratios etc etc.... when in all honesty just some common sense needs to be applied.

My experience has been that DSB work great for certain applications however they must be used properly and properly maintained. They are not something that can just be chucked in and left to their own devices and they do a lot more than just reduce nitrate and phosphate.

By maintained I don't mean syphoned or cleaned or refreshed with fresh sand etc etc... I mean populated with the correct fauna and flora which will assist carry out the complete removal of "nutrients" accrued in the sand over time.

A deep sand bed firstly needs to be set up properly with the correct grades of biologically active mud, sand and grades of small particle gravel. It then needs to have the correct fauna added to it and observed. Each grade or zone within a deep sand bed is a habitat in its own right for a very different group of bacteria micro or macro fauna... each having their own role to play in the break down of organic matter.

DSB are highly complex ecosystems and if not in balance will produce results which are considered unfavorable.... a car is a time bomb if not driven properly!!!

DSB placed in the display tanks have proven for me not to be suitable in SPS tanks when fish are present. Colouration of corals typically effected.

DSB are great tools for certain applications and if managed well are highly effective for nutrient reduction, process ridiculous amounts of detritus and generate large amounts of micro fauna and plankton....

What are the correct grades? How to obtain biological "active" mud of the correct grade? What may be the correct fauna?

Compared to a simple small easy manageable bio-filter the capacity to reduce nutrients of a DSB seems to be very limited.
How the reduction rate of a DSB can be managed?
For me a DSB is more a producer and consumer as it is a reducer. I would provide a DSB for keeping animals and organisms which need a deep bottom and may contribute to the balance in the system or and may be part of the display, not for exporting nutrients ( nitrogen?) especially as for this purpose a cheap simple small easy manageable bio-filter is a lot more effective and more reliable.

 

[Craig Stuart - Reefscaper]

Some great questions here Belgian and many topics address in the questions posed ranging from what nutrients are being processed to biodiversity. Not sure really where to start. Type and quantity of biologically active mud (typically mangrove mud or reef sediment), grades of live sand and or larger coral or stone particulates all depend on the system and the species of animals it is designed to exhibit...

While I can't agree that the capability of a DSB to reduce "nutrients" (not sure what you mean by nutrients here) is limited. I would agree that for a reefer simply wishing to manage nitrate and phosphate levels... other methods are easier to manage and measure the performance of.

Thats said, DSBs (when appropriately set up and managed) are very effective.

 

[Belgian Anthias]

I think most reefers who consider using a DSB do so for the denitrifying capacity attributed to a deep sand bed and for determining the depth and the granule thickness of the bed to be used think mainly in function of the denitrifying capacity and less in function of the future residents.
Since it is not specified which nutrients are meant, it can be assumed that, apart from a bit of nitrogen that is effectively removed, little or no nutrients are effectively removed.
A DSB can be considered to be effective in reducing ammonium and recycling organic substances, mineralizing them, making them available again as inorganic substances for further use. Some of these substances will form chemical compounds with the media used, bio-chemical processes may decompose it, depending on the substrate used. All of this will also happen in a normal sand bed of +- 2.5-4 cm, including denitrification! Increasing the layer thickness will result in the denitrifying capacity of the bed being increased, which is not the same as an increase in denitrification. The risk of completely oxygen-free zones will also increase considerably.
If with the lowering of nutrients the export of these substances is meant one will have to be satisfied with the removal of an undefined amount of nitrogen.
Since a DSB does not give me any control over the amount of nitrate that can or will actually be removed, which is very easy to achieve making use of a BADES bio-filter, I would only consider using a DSB to provide the needs of a target group.

 

[Craig Stuart - Reefscaper]

I think most reefers who consider using a DSB do so for the denitrifying capacity attributed to a deep sand bed and for determining the depth and the granule thickness of the bed to be used think mainly in function of the denitrifying capacity and less in function of the future residents

Hmmm ...many use them for much more too. My point was they sometimes get a bad rap.

Since it is not specified which nutrients are meant, it can be assumed that, apart from a bit of nitrogen that is effectively removed, little or no nutrients are effectively removed.

This can not be assumed, sorry. Lots of documentation to the contrary.

Some of these substances will form chemical compounds with the media used, bio-chemical processes may decompose it, depending on the substrate used.

Depends on many factors not just the media.... however yes.

All of this will also happen in a normal sand bed of +- 2.5-4 cm, including denitrification! Increasing the layer thickness will result in the denitrifying capacity of the bed being increased, which is not the same as an increase in denitrification. The risk of completely oxygen-free zones will also increase considerably.

Much again here depends on your definition of "normal", the sediment, grade size and composition, fauna, flora, fungi population etc etc of the DSB....

Not sure what the risk is you are alluding to of oxygen free zones - Potential for further reduction of nitrate or formation of toxic sulphur based compounds?

If with the lowering of nutrients the export of these substances is meant one will have to be satisfied with the removal of an undefined amount of nitrogen.

Not following the logic here sorry....

Since a DSB does not give me any control over the amount of nitrate that can or will actually be removed, which is very easy to achieve making use of a sulphur based bio-filter, I would only consider using a DSB to provide the needs of a target group.

I'm sensing that you are a sulphur based bio filter fan....?

 

[davocean]

I have had many really nice tanks that had DSB, totally agree if you set up properly and maintain properly they do just fine.

My intention of running a DSB was not really so much for denitrification, but it was primarily for the sand dwelling animals I keep, and any denitrification was just a side benefit.

If you are setting up a DSB solely for denitrification, a remote would be a good way to go.

I have had shallow, and DSB tanks that all have worked just fine, same as the many that have done BB tanks for their own reasons.

I build my tank specifically for the animals I plan to keep in it, how we manage nutrient or other issues may vary depending which set up and route we take in doing so.

 

[jda]

These last few posts have more of a sense of "reading about" a DSB and not so much "using one."

The depth of the sand does not matter too much... anything over 3 inches, IME, will denitrify down to just below 1 PPM of nitrate... never to zero, but also rarely above 1. The sand using critters appear to be find with 2 inches, or more... also IME. I got a single cucumber about 6-8 years ago with a 2 inch mixed grain sand bed and now I have 6 cucumbers that I can see.

 

[Craig Stuart - Reefscaper]

JDA, sorry to disagree with you... but depth and particle size matter a lot.
Your cucumber might shrink somewhat if you left flopping around on A 6" bed of 1/4" coal rubble for long...
DSBs are effective, sometimes over simplified and at times get a bad rap.