Sand - composition and effect

Discussion in 'Biological/Natural Filtration and Deep Sand Beds' started by sunburst, 14 May 2008.

  1. sunburst

    sunburst

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    For those using silica (playsand) or beachsand i found this a great explanation of the available substrate choices and the implications



    Mods This is an exert from a article from REEFKEEPING.COM written by Tom Murphy. If there should be any copy right implications please delete.



    Mr. Sandman, Bring Me a Dream
    When using all live sand there is no problem setting up the tank, well, except the cost. Many reefkeepers feel it is a little too steep. The usual solution has been to use base sand (dead sand) and mix it with live sand. This method does work pretty well and, in years gone by, there was Southdown Tropical Play Sand to the rescue. Why Southdown? Well, true live sand is actually a mineral called aragonite. It is composed of calcium carbonate composed mainly of shells and skeletons of dying reef creatures over hundreds or thousands of years. The advantage of aragonite is that it not very dense (specific gravity ~2.94), lacks sharp edges and has buffering capability (can neutralize acids). Since it very abundant and natural to the reef environment, it is perfect as base sand. That was the wonder of Southdown; it was pure aragonite and available at the hardware store for under $10 for a 50 pound bag. It was perfect - and then they stopped marketing it. It is so rare today that threads continually pop up citing appearances that, like UFO’s, are never confirmed.
    You can still buy aragonite sand but usually only at the local fish store (LFS). It does cost a lot more than Southdown, but it is still true aragonite. “Live sand” in bags, also sold at the LFS, is something to avoid, however. It is just a bag of dead aragonite, with some nutrient solution added, and a few cultured bacteria. It’s artificial from the word “GO” and lacks all those tiny, sand-shifting organisms so important to a great deep sand bed. It is rarely worth the extra money.
    The question arises, “If cheap aragonite is not available, can other sands be used?” The answer is yes. While not as perfect for your tank as true aragonite, they too can be used as base sand. First off, it must have the proper size, in the range of 0.05-2.0 mm. The majority of the particles should fall in the range of 0.15 through 0.25 mm; about the same size as fine-grained, granular sugar. Some, not all, silica sands can be found that meet these criteria. Usually that will be found in silica play sand or sand box sand. The major drawback is they are denser and have relatively sharp edges. They also offer no buffering ability at all.
    Let me talk a bit about buffering. Once oxygen is depleted in the bed, anaerobic organisms appear. These guys process the food they consume mainly by using fermentation - “Cheers!” Yes, they do make alcohol but carry it out too far. You end up with organic acids, like vinegar, a completed fermentation by-product. Now, pour some vinegar over aragonite and it fizzes like an Alka-Seltzer. This is because the acid, vinegar, reacts with the base, calcium carbonate, and produces a neutral salt - calcium acetate. The net result is that some sand dissolves but the acid is neutralized.
    There is a side effect, however. The reaction also produces free carbon dioxide that, dissolved in water, produces a weak acid, carbonic. In a perfect world this would reduce the bed’s pH below 6.5 where the carbonic acid reacts with the calcium carbonate in the aragonite forming calcium bicarbonate; a very good thing as it adds calcium into the water column.
    Alas, it is not a perfect world. In the days of yore it was claimed that having a deep sand bed was the way to go as it provided all the calcium a tank would need. Sadly, this is not the case and having a deep sand bed is not the road to having a calcium-dominated tank. Only a small extent of the sand bed meets these conditions and the amount of calcium dissolved will nowhere meet the calcium requirements of most hobbyists’ tank. Yet, I’m always the optimist and, even though small in its contributions, every bit helps.
    Notwithstanding, silica sand does work. It was once thought that silica sand would release untold amounts of silicates into the water column, thereby fostering a continual diatom outbreak. Sand is a major component of the glass in your tank, and if it dissolved, be prepared for a flood even Noah can’t endure! Silica sand is inert.
     
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  3. Warr7207

    Warr7207

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    Nice article, very interesting
     
  4. SIMS

    SIMS

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    yes thanks :)
     
  5. viper357

    viper357 Admin MASA Contributor

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    He's basically just saying what we already know, isn't he? That aragonite is not a feasible means of maintaining calcium in our tanks and nor is playsand. Also that playsand/silica sand does not cause diatoms.

    A link to the original article will solve that issue.
     
  6. Mekaeel

    Mekaeel Moderator MASA Contributor

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    Thanks for the article Sean :)
     
  7. lanzo

    lanzo Sponsor

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    koo beans:thumbup:
    so playsand is good to go in any students tank.... YES!
     
  8. Warr7207

    Warr7207

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    Just remember to seed it
     
  9. lanzo

    lanzo Sponsor

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    yip, my next tank will be a DT DSB with playsand, can't wait( one day)
     
  10. jacquesb

    jacquesb Retired Moderator

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    Ditto Lanzo! As Viper said - I was ALWAYS preaching as much. Sorry that I am never quoted ;-)
     
  11. Alfie

    Alfie

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    Who is Tom Murphy? How can you compare silicates in the sand compared to the glass that has been treated and processed. What studies has he done on this for reference?
     
  12. Reef Maniac

    Reef Maniac MASA Contributor

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    Further to the above, we had quite an interesting discussion on this topic back in January - here's a link to the thread: Deep sand bed - Hennie's Corner

    Hennie
     
  13. Alfie

    Alfie

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    Hennie that is a great thread and DLSB is 100% fantastic, but I think the discussion here goes aroung silicate sand and aragonite and which of the 2 is beneficial. Would you say it is OK to add silicate sand to your system as per the indication or would you rather use silicate sand as the author has indicated that it has no negative effects?
     
  14. sunburst

    sunburst Thread Starter

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    Great thread Hennie. Would also like an opinion on Alfie's observations. Thanks Alfie. Yes... composition and effect. And the question that needs answering relate to effect. They both do the job. But what are the positive effects of one over the other, if any.

    PS The author does not subscribe to silicate. He merely points out that silicate is inert
     
  15. Alfie

    Alfie

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    Notwithstanding, silica sand does work. It was once thought that silica sand would release untold amounts of silicates into the water column, thereby fostering a continual diatom outbreak. Sand is a major component of the glass in your tank, and if it dissolved, be prepared for a flood even Noah can’t endure! Silica sand is inert.[/quote]

    Though he says it it is inert he is questioning the release of silicates as indicated and I would like to know if this is or is not the case as he is comparing it to the glass.
     
  16. sunburst

    sunburst Thread Starter

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    Inert it is. Or certainly in the space occupied by our lifetimes. The chemistry of silicone is almost as diverse as carbon. However Siloxanes on the other hand is a group of silicone's that IMO could be the culprits of unexplained algae issues.
     
  17. Reef Maniac

    Reef Maniac MASA Contributor

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    In short, YES - you can safely add silica sand to your system. Let me elaborate a bit...

    The 'aragonite sand is the best' statement has been hijacked by the advertising people, and is really a sales gimmick, in my humble opinion. Although aragonite does release some calcium at our tanks' pH levels (albeit quite a small amount...), this is it's only advantage over silica sand. The sand gradation (particle size distribution) is a much more important aspect to the success of our tanks than the addition of a small amount of calcium, which can easily be added by some other means.

    Here are a few extracts from an excellent article by Dr. Ron Shimek Ph.D, published in Reefkeeping online magazine: How Sandbeds REALLY Work by Ronald L. Shimek, Ph.D. - Reefkeeping.com

    I could be wrong, but IME most 'aragonite' and 'crushed coral' sand particles are *much* larger than 0.25mm, and as such make a rather poor substrate for a DLSB. I would much rather lose the questionable benefit of the small calcium addition of aragonite sand, and have a thriving, diversely populated LIVE sand bed.

    As for the silica sand releasing silicates into the water which could feed diatoms, let me refer you to an article written some years ago by Dr. Craig Bingman, Ph.D (a rather well known chemist who should know his stuff...), and published in the now defunct Aquarium Frontiers website Aquarium Frontiers Feature:


    He concludes his article with the following golden nugget:

    Hennie
     
  18. jacquesb

    jacquesb Retired Moderator

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    You da man Hennie! You da man! Enjoyed this read, once again! ;-)
     
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