I'm thining about installing a silica based deep sand bed?

[Highland Reefer]

I've been having some nitrate problems & have researched the deep sand beds. I was thinking about buying a 100 gallon rubbermaid tank & making it into a refugium with a deep sand bed. I would need to put a lot of sand in there and can not afford to buy the argonite based sand. I have already looked for a local cheap source of this sand and can not find any anywhere. Since I have made many costly mistakes before, I thought I would throw this out for discussion. Any imput would be appreciated.

[jamal]

silica will leach and grow diatoms for a long time if not indefinitely.

[shawns]

i was told that you need the larger substrates to make a dsb work. silica sand is most likely too small to function properly as a dsb.

[gastone]

I hear that both the glass that we use in our aquariums and "silicone" are silica based... I'm not aware of them leaching any silica either. I say bunk. I don't use silica sand as I used southdown back when it was available. That being said, I wouldn't hesitate using silica sand in my fuge or RDSB in the future.

 

I figure by the time my future silica sand degrades into silica my tank walls and silicone will have disappeared and I won't have a tank to speak of.

 

Garrett.

 

FWIW as it isn't "intended" for aquarium use I would rinse really well.

[treesprite]

I have read in a couple places that silica sand does not leach anymore than the glass or silicone seal. Who has ever trully experimented with this? Who is to say that someone who had diatom problems didn't have them for some other reason (like tap water or bad ro?)

[F&Fmgr]

i had a deep sand bed of silica based sand and it was fine for the first year then i noticed some really nasty chemical issues in the system....I can only contribute it to the grain size and the lack of diffusion that occurs with fine grain silica sand. I pulled it and replaced with aragonite and all my problems were non existent in about two months...( the time i figure it took for the DSB to repopulate)

 

Just my two cents

 

Sean

[dshnarw]

I hear that both the glass that we use in our aquariums and "silicone" are silica based... I'm not aware of them leaching any silica either. I say bunk. I don't use silica sand as I used southdown back when it was available. That being said, I wouldn't hesitate using silica sand in my fuge or RDSB in the future.

 

I figure by the time my future silica sand degrades into silica my tank walls and silicone will have disappeared and I won't have a tank to speak of.

 

Garrett.

 

FWIW as it isn't "intended" for aquarium use I would rinse really well.

 

nope...not bunk. The structure of the silicon-oxygen bonds in silicone sealers and aquarium glass is different from the quartz in silica-based sands. The amount of surface area on the sealant and the glass is also very small compared to the amount of surface area in the sand. Those two factors mean that the sand will leach much more (and more quickly) from the sand than the glass and sealant.

 

Problem 2 - silica based sand is not pure, like aragonite-based sands "mined" from the ocean. Silica sands are produced a number of ways, but the most common is the mine them from a quarry. They are usually poorly rinsed, and dumped in the bag. If there were natural contaminants in the groundwater (arsenic, for example, is a very common groundwater pollutant), it'll still be in the sand. If the truck leaked some oil or gas when it droppped it's load, it'll be in the sand.

 

I have read in a couple places that silica sand does not leach anymore than the glass or silicone seal. Who has ever trully experimented with this?

 

even if this were true (it's not exactly), the surface area difference alone will contribute to the leaching process greatly. This is simply a kinetics issue. Solubility of silica in distilled water is 6ppm at room temp/pressure. It will be slightly higher in seawater due to higher pH and the presence of dissolved ions. There's no experiment needed beyond what chemistry/geology has already discovered - run *PURE* water over a piece of glass, sealant, silica sand, what have you, and the equilibrium will reach 6ppm in the water. The difference is in kinetics - the glass and sealant have low surface area, slightly different structures, so they reach equilibrium slower. Silica sand has a high surface area, it reaches equilibrium faster.

Edited March 2, 2008 by dshnarw

[treesprite]

I only know that I wouldn't try something that takes so much skepticism with it.

[lancer99]

It will be slightly higher in seawater due to higher pH and the presence of dissolved ions.

I am certainly no chemistry major, but wouldn't silica dissolve more quickly in freshwater than salt, since it has less ionic competition?

 

There have been a number of threads about using silica sand recently on RC, and the general consensus seemed to be that it's fine...but you have to pay attention to the type of sand. Some of them consist of shards, which don't support the development of infauna, like sugar-sized aragonite sand does.

 

My 2 cents, FWIW (2 cents )

 

-R

[Highland Reefer]

It is nice having a PhD student in Geology who is Interested in volcanic/magma chamber processes, ore mineral deposits, and the effects of volcanic systems on coral reefs around when you need them. I appreciate your help. I was about to make a mistake. The older references I had read were not from geologists:

 

"Very successful tanks may be set up utilizing black lava sand, or fine siliceous sand, as long as the grains are of the appropriate size." By Ronald L. Shimek, Ph. D.

 

"All of the arguments against soluble silica being released from "silica" sand can be easily refuted, and I have done so in the past." Randy Farley-Holmes Ph. D.

[gastone]

Daniel,

 

it is my understanding that quartz is insoluble in water.

 

After being humbled by you (BTW, for all I know you could be making this up. I don't know your credentials, but I did in fact sleep in a Holiday Inn Express last night) I found this article: http://www.advancedaquarist.com/issues/jan2003/feature.htm

 

Well aware of other possible contaminents in silica play sand. I've got around 400# of southdown in my sump. At the going rate of ~$1/1# of aragonite sand these days that would cost me $400. If I went with silica sand I could do it for $20 and a couple hours of rinsing. I don't think anyone will be able to assure me that "reef sand" is without contaminents itself. Since I'd be rinsing anyway, I'll do the silica sand.

 

g.

[mogurnda]

Have had a silica DSB in my 90 for 4 years. No more diatoms than my tanks with aragonite substrates. One can argue theory all day, but, as one of my old profs used to say "empirical data is a very powerful tool."

[dshnarw]

I am certainly no chemistry major, but wouldn't silica dissolve more quickly in freshwater than salt, since it has less ionic competition?

 

Yes and no. It dissolves more easily in freshwater than saturated or nearly saturated water, because there's no place for the ions to "bond" with the water via hydrogen bonding or van der Waals forces - they've all been taken by other molecules/ions. In very pure water, all of the water is tied to other water molecules via hyrogen bonds, creating a 3-d structure. For something to dissolve, it must break apart the hydrogen bonds, which takes some amount of energy.

 

After you get some ions into the solution, you've broken enough hydrogen bonds between the water molecules that subsequent additions of ions need not expend energy breaking those bonds - it's already been done. So, they can create their own bonds with the water more quickly and with less energy.

 

It is nice having a PhD student in Geology who is Interested in volcanic/magma chamber processes, ore mineral deposits, and the effects of volcanic systems on coral reefs around when you need them. I appreciate your help. I was about to make a mistake. The older references I had read were not from geologists:

 

"Very successful tanks may be set up utilizing black lava sand, or fine siliceous sand, as long as the grains are of the appropriate size." By Ronald L. Shimek, Ph. D.

 

"All of the arguments against soluble silica being released from "silica" sand can be easily refuted, and I have done so in the past." Randy Farley-Holmes Ph. D.

 

Oddly, we've gone over this subject in regards to ore systems in my Economic Geology course recently

Quartz is the dominant mineral in nearly all ore deposits, so silica behavior is the easiest way to study conditions for emplacement.

 

Happy to add to the conversation, and use all this education I've been paying for

[dshnarw]

Daniel,

 

it is my understanding that quartz is insoluble in water.

 

After being humbled by you (BTW, for all I know you could be making this up. I don't know your credentials, but I did in fact sleep in a Holiday Inn Express last night) I found this article: http://www.advancedaquarist.com/issues/jan2003/feature.htm

 

Well aware of other possible contaminents in silica play sand. I've got around 400# of southdown in my sump. At the going rate of ~$1/1# of aragonite sand these days that would cost me $400. If I went with silica sand I could do it for $20 and a couple hours of rinsing. I don't think anyone will be able to assure me that "reef sand" is without contaminents itself. Since I'd be rinsing anyway, I'll do the silica sand.

 

g.

 

"Insoluble" is a general term that is applied for the basis of understanding objects that have very low solubilites. As mentioned in the article you linked, the maximum solubility of silica is ~11.2 ppm - next to nothing compared to Ca, Mg, Alk... The problem, IME, comes in when you consider the biological aspects of this - what benefits from the excess silica in the tank, and do we consider that a nuisance species? RHF's best point in the article, IMO, is that he didn't have any issues with the inhabitants that benefited from it - but realistically, we don't know if that means he didn't mind some diatoms (or he cleaned the tank enough that he never noticed them?). That said, the biological aspect I cannot further comment on.

 

 

Have had a silica DSB in my 90 for 4 years. No more diatoms than my tanks with aragonite substrates. One can argue theory all day, but, as one of my old profs used to say "empirical data is a very powerful tool."

 

And what are the rest of your parameters, your filtration, livestock, etc? Your cleaning schedule? What other hitchhikers are in the tank?

Observations are only empirical if they have context

[jason the filter freak]

I had a 55 with silica in the main display for well over a year no datom issues to speak of. I also say bunk

[Highland Reefer]

Daniel,

 

Ronald L. Shimek further stated that the diatoms could be controlled by using proper tank inhabitants. He did not say which ones. It seems to me that if you have a large sand bed that nothing would be able to keep up with the amount of soluable silicon. Randy Farley-Holmes goes on his articles to imply that it could be made work also, but did not explain that in any of the articles of could find. You refered to different tank inhabitants in a system in this thread.

 

I take it in your mind that using silica sand is out of the question & I should just save up my money & bite the bullet for the expensive sand.

[traveller7]

A couple of issues with the dialogue:

 

1. A remote deep sand bed in a garbage can/bucket should not have sand critters or light added. We just want prefiltered high water flow, no way for detritus to settle, and denitification. Shimeks arguement on grain size is moot in this case. Better to look toward Calfo's concepts for the application.

 

2. Have used silicate sands, ceramics, plastics, oolithic arag, etc., and can't tell the difference in diatoms or any other slimes; but then I use a shovel to feed my fish and YMMV :D

[Highland Reefer]

A couple of issues with the dialogue:

 

1. A remote deep sand bed in a garbage can/bucket should not have sand critters or light added. We just want prefiltered high water flow, no way for detritus to settle, and denitification. Shimeks arguement on grain size is moot in this case. Better to look toward Calfo's concepts for the application.

 

2. Have used silicate sands, ceramics, plastics, oolithic arag, etc., and can't tell the difference in diatoms or any other slimes; but then I use a shovel to feed my fish and YMMV :D

 

 

 

DSB - Deep Sand Bed Potential - By Anthony Calfo

 

 

For many years, we have seen the use of substrates in marine aquaria wax and wane in popularity. The issue has run the gamut from bare bottom through shallow bed to deep sand, and then back to bare bottom again. But even with the acceptance of truly deep sand beds in America by the mid 1990's, DSBs did not see regular use until refugia were established some years later. The reasons are obvious, perhaps: refugia are smaller, more affordable and less risky "models" of deep substrates, which the average hobbyist can attempt with greater confidence. But even with fears aside, the addition of a deep sand bed to a full display (versus a small refugium) is an investment in labor and money. It is no wonder that the large-scale DSBs took some time to be accepted.

 

 

As the popularity of DSBs grew, the number of critics did too. Sadly, many of the most outspoken detractors argued in theory without even trying a DSB! And the majority of the rest of the critics seemed to unfairly blame their aquarium failures on their very limited DSB experiences. The more likely cause of their failures was from typical bio-overloads, poor water flow, and neglect of water quality.

 

 

The reality of successful DSP applications, however, is amazingly simple, albeit strict. For perspective, I can tell you that my experience with living substrates is not insignificant. I utilized 48,000 lbs (over 20,000 kg!) of fine sand for my coral farming greenhouse operation and have installed similar deep sand beds in over one hundred private aquariums for over ten years. In this article, I will share with you a very practical survey of the potential - and the limitations - of a deep sand bed application.

 

 

If I had to reduce the summary of challenges of deep sand bed applications to a single statement, I would have to say that new hobbyists have unrealistic expectations for what a deep sand bed can do. That is not to say that a deep sand bed does not have great potential! They truly do. But many people seem to have extremely high expectations for new sand to become teeming with life almost overnight in aquaria. Such a thing is difficult and requires careful orchestration, time and patience to happen. But more often, it fails because of impatience; aquarists stock DSB aquariums too quickly with predatory fishes that consume the foundling populations of desirable worms, microcrustaceans and other sand fauna, before the sand life can adequately populate to sustain predation. That is an enormous mistake. The inferior biotic faculties struggle to process the all-too-common overload of fishes, food and waste in aquaria, and the DSB fails in such circumstances.

 

 

A similar problem occurs in DSB systems with inadequate water movement that allows too much particulate waste to sink and accumulate excessively in the DSB over time, causing the aquarium to "crash." Instead, we should aspire (in bare bottom and DSB aquaria alike!) to always keep reef-like water movement with strong flow that keeps solid matter in suspension longer for greater feeding opportunities by the filter feeders and better processing by skimmers and other filters. Strong water movement in the aquarium is the number one key to success with long-term healthy DSBs. I recommend "sps-style" water flow of near 40-60 X turnover of the tank display for best results.

 

 

I can remember in the early days of reef-keeping in America, we would hear stories of great German aquarists that would keep their new live rock (for "Berlin" style systems) in the dark for six months or more with good water flow and supplementation (organic and inorganic). The purpose was to dramatically improve the quality of "cured" live rock with greater coralline algae and more life forms before lights and fishes were applied. Few American aquarists had the patience to do this at the time, but I think we must have admired the German stony coral displays so much and remembered the lesson that we apply it now to our refugia and DSBs. Now, with thanks and respect, we remind our European friends of this same patient advice: avoid adding predatory fishes or corals to DSB systems for many months to allow adequate populations of infauna to develop.

 

 

You will notice that these two fundamental pieces of advice are different from what most retailers and so-called experts will recommend. Both mistakenly tell you to add "clean up" organisms from the very beginning (note: at least one of those two people profit from this bad advice ). But the addition of predatory snails such as Whelk (Buccinid), Murex (Muricid), Mud (Nassarid) and Tulip (Fasciolariid) can be devastating to the desirable life forms in the sand of an aquarium. The popular Conch species (Strombids) are even worse as most will starve to death not long after they have decimated the infauna of a DSB. Of similar concern is the use of Holothurid "Sea cucumbers" (and Sand-dollars) and all of the sand-sifting gobies. These vigorous sifters destroy a lot of biomass in the substrate. Worst of all perhaps are the alleged "reef-safe" hermit crabs; these crabs are brutally indiscriminate predators on desirable sand bed life forms. The only thing that any of these aforementioned "bad" DSB organisms are actually good for is tilling the sand surface to prevent the buildup of brown diatom algae. But you can use a number of safer organisms to accomplish algae control without destroying DSB biodiversity!

 

 

Best bets for DSBs include: Stomatella-type "paper shell" snails, Ceriths (Cerithium and close kin) and most all errantiate polychate worms. Yes

[Sharkb8]

Yes and no. It dissolves more easily in freshwater than saturated or nearly saturated water, because there's no place for the ions to "bond" with the water via hydrogen bonding or van der Waals forces - they've all been taken by other molecules/ions. In very pure water, all of the water is tied to other water molecules via hyrogen bonds, creating a 3-d structure. For something to dissolve, it must break apart the hydrogen bonds, which takes some amount of energy.

 

 

Anyone who can spell van der waals properly is A OK in my book !!!

 

I'm just a Ph.D. in biochemistry (postdoc in o-chem) so I can't contribute much to this inorganic discussion, except to vouch for Daniel here. I've never met him but he's definitely got my vote!

 

Oh, and I have a DSB but I have no idea what its made out of (bought it, and the tank it was in on Craig's list).

 

Tom

Edited March 3, 2008 by Biodork

[dshnarw]

Daniel,

 

Ronald L. Shimek further stated that the diatoms could be controlled by using proper tank inhabitants. He did not say which ones. It seems to me that if you have a large sand bed that nothing would be able to keep up with the amount of soluable silicon. Randy Farley-Holmes goes on his articles to imply that it could be made work also, but did not explain that in any of the articles of could find. You refered to different tank inhabitants in a system in this thread.

 

I take it in your mind that using silica sand is out of the question & I should just save up my money & bite the bullet for the expensive sand.

 

 

No, I don't mean it to sound that way. It certainly isn't out of the question, but it does have more "risk" involved in using it that you should be aware of - that it will cause an increase in silica, and that the risk of contamination of the sand is higher.

 

Contamination is generally easy to solve - buy the "purest" looking sand you can get, and test for contaminants (phosphate, ammonia, nitrate, and heavy metal tests like copper you have on hand) after dropping it in a bucket of DI water with a powerhead for a couple of weeks.

 

The missing link, IMO, is whether high silica in solution actually means the presence of diatoms, and what can be done if it does. This is where my argument with mogurnda's use of the word "empirical" lies, and all the other comments that their tanks didn't have diatom problems. Is this because of some filtration method, or other organism in the tank (either eating diatoms or out-competing the diatoms)? Or, does the commonly mentioned high silica=diatoms not really hold true? Without knowing all the parameters of each system (context), we don't have empirical evidence of anything beyond *something* worked.

 

That said, I think Shimek's/RHF's articles may shed some light on at least the "other organisms" part. I think the proper tank inhabitants would cover the two issues - eat the diatoms, or outcompete them for silica. For eating the diatoms, I would assume snails, possibly some fish?, and echinoderms - urchins, some stars. For outcompeting, some sponges (this was my earlier reference) requre silica to produce spicules.

 

Regarding the ability to keep up with silica in solution - organisms should be able to keep up fairly well. Consider the amount of waste produced each day, and yet no ammonia is present. Or that calcium an alkalinity dosing is requred in SPS dominated tanks on a constant basis - the stony corals in my tank remove 10s of ppm of calcium and alkalinity daily.

 

 

So, to conclude - you could certainly use it...with care/caution (definitely don't dismiss the possible *bad* outcomes right off the bat without considering the remedies for those outcomes). Were it me, I'd be buying up all the old sand that pops up for sale and rinse the heck out of it, and spend a bit more to avoid possible issues.

 

Anyone who can spell van der waals properly is A OK in my book !!!

 

I'm just a Ph.D. in biochemistry (postdoc in o-chem) so I can't contribute much to this inorganic discussion, except to vouch for Daniel here. I've never met him but he's definitely got my vote!

 

Oh, and I have a DSB but I have no idea what its made out of (bought it, and the tank it was in on Craig's list).

 

Tom

 

Thanks

 

(excuse me while I shudder at the thought of organic chem...)

Edited March 3, 2008 by dshnarw

[dshnarw]

forgot one important possible "competitor" for silica - bristleworms.

 

(possible because I haven't seen an article stating this, but seems to be fairly common speak in the various forums)

[Highland Reefer]

To be honest, I didn't think that I would gain much knowledge about this subject from my post. I am pleasantly surprised. We have a great group of people in this organisation and I am proud of that fact.

 

My sincere thanks.

[traveller7]

Aquarium hobbyists usually find calcite sand beds to be the best choice for aesthetics, price, availability and required husbandry; all are moderate.[/color]

fwiw: PetsMart seems to be liquidating the seachem sands, might want to drop by and check out a few locations. I picked a few 20 and 22lbs bags up for $6.99 ea this weekend.

[mogurnda]

The missing link, IMO, is whether high silica in solution actually means the presence of diatoms, and what can be done if it does. This is where my argument with mogurnda's use of the word "empirical" lies, and all the other comments that their tanks didn't have diatom problems. Is this because of some filtration method, or other organism in the tank (either eating diatoms or out-competing the diatoms)? Or, does the commonly mentioned high silica=diatoms not really hold true? Without knowing all the parameters of each system (context), we don't have empirical evidence of anything beyond *something* worked.

This is what I meant: I have used a silica DSB, and am not compuslive by any means (and feed with a trowel), yet the dreaded diatom bloom has never materialized. As far as I can tell, all the hand-wringing about silica sand beds is based on the idea that dissolved silica will automatically cause a massive diatom bloom, not on any actual observations. If people chime in that they had bad experiences with silica beds, then I will stand corrected.

 

All of my tanks have always had a little diatom growth, which is fine by me. They come right off with the mag float, and are the preferred food of most of the herbivorous snails we keep, as well as many blennies and some tangs.

 

I always feel mixed about these kind of discussions. As a scientist*, I like to see people thinking hard about these issues, but the plain fact is that there is just about zero real data because every tank is different and nobody wants to take the time and effort to set up 10 identical reef tanks to do proper controls. The best I can usually do is find out whether something I want to try has been a success or disaster in others' hands.

 

In all honesty, I will probably replace my silica bed over the next year. Silica is greyer and not as pretty, and it is heavier so it compacts more.

 

*Not a chemist, just a biologist who spends a third of his life dealing with chemistry.

[gastone]

speaking of silica, despite this discussion I totally forgot that about a year ago or so I accidentally dumped about 500g of silica beads in my tank that i was using as a dessicant for my ozone. Oopsy. I contacted the guys on the chemistry forum on RC here

 

No issues to date that I'm aware of.

 

G.