The Science Of Sand Washing

mfinn

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For practical purposes, put 3 to 4 inches of sand in the bottom of a 5 gallon bucket. Stick a hose in the bottom, constantly move it around and rinse until the overflowing water is clear. You can do a pretty darn good job - not perfect, but really good. For a 20 lb sack of sand, I do 1/3 to 1/4 of the bag at a time.

With larger particle sizes, you can get the stuff almost perfectly clean.

This is not a good idea if your tap water is horrible and you are worried about what nasty compounds will bind to the aragonite.

I read this method from ReefmanRon a long time ago and it is the best that I have ever seen.
I've always used a long plastic/rubbermaid type storage box ( 16" wide x 30" or so long, x 10" tall ,give or take a few inches either way ) and dumped 1/4 to 1/3 of a bag in it and run the garden hose in it like a sluice box. Having a slight hill to work on and almost a requirement for me is to do this on a hot day.

Seems like a pretty simple subject and not worthy of all this "science".
 

Apollomax

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Not too long ago I made a claim about needing less water to wash new aragonite sand if you first sieve it to remove the fines.

https://www.reef2reef.com/threads/quit-wasting-water-washing-dry-aragonite-sand.953390/

Long story short, I was wrong. So, I went back to the lab to understand aragonite sand washing. Here is the new data that gives us insight into why aragonite sand is nearly impossible to rinse clean.

Everyone who has ever tried to wash aragonite sand until the wash water ran clear, faces performing what seems like an infinite number of washes. The orange line on the plot below shows how the cloudiness of the wash water (measured with the Hanna Color of Water Checker) declines rapidly at first but then refuses to budge much lower.

602CAC02-A9D1-4DBB-8BE0-51DC8CF64C8C.png


I initially thought that removing the fines by sieving the sand first would solve the problem of “infinite washes”. The blue line in the above plot shows it does not help. What is going on?

One of the first hints about what is happening during aragonite sand washing came from comparing data from two sand washing experiments. By overlaying the turbidity data from washing 100 mL and 200 mL of sand, the process looks like it might involve two stages. The first stage is where the turbidity is correlated with the initial sand mass while the second stage seems to occur with little or no difference between the two initial sand masses. The correlation of the first stage turbidity with the initial sand mass suggests turbidity is relates to the amount of fines suspended in the wash water, while the second stage turbidity, seemingly unrelated to the amount of sand present, means what?

55D7BEE0-C604-4201-8451-4729A4EC6EBF.png


To investigate the process in the second stage further and determine whether it occurs throughout the entire sand washing exercise, the turbidity of the wash water was measured, then it was filtered through a 1.6 micron glass filter to remove the fines. Each filter was weighed before use and then again after filtration and drying. Turbidity of the filtrate was also measured to assess how much turbidity there was that was not associated with the fines in the sand. Comparing the turbidities of the wash water and filtrate (see plot) demonstrates that the second turbidity generating process occurs in every wash.

B330436F-B6CE-43AF-89EF-5EB828AF8429.png


Comparing turbidities of the filtrate against the wash water turbidity minus the filtrate turbidity indicates that the decline in turbidity caused by fines might be faster (orange line) than the decline in turbidity caused by the second stage process (blue line).

F5EFD846-BC1C-492D-82C1-0A8D4CBFABA1.png


With regards to the mass of the filtered fines, it is well correlated to the turbidity of the wash water (see plot). The intercept is not zero pribably because of the turbidity caused by stage two turbidity.

57A9BD40-4057-477F-8925-4B179942D838.png


Data that gave me a hint about what might be happening in the second turbidity generating process involved stirring washed sand in tap water for varying lengths of time (see plot below). This data makes clear that wash water turbidity rapidly increases with the time that sand is exposed to tap water. Interestingly, stirring aragonite sand for one hour in tap water resulted in wash water resembling a thin, translucent white paint. This last observation suggests that a crystallization or precipitation is occurring. But why?

8809F309-1F85-49D8-AE9C-676F8B64F479.png


The sand used in the experiments contains aragonite, a form of calcium carbonate. Calcium carbonate has two major polymorphs or crystal forms, aragonite and calcite. Aragonite is typically formed by living organisms and is less stable than calcite, just like diamond is less stable than graphite. A manifestation of calcite stability is its lower solubility in water compared to aragonite. The consequence is that when aragonite dissolves in water (calcium carbonate is slightly soluble in freshwater), the concentration of calcium carbonate exceeds the solubility limit of calcite and crystals form. This dissolution-crystallization process can continue as long as there is aragonite present because crystallization continually removes calcium carbonate from solution, allowing more aragonite to dissolve. Stirring aragonite sand for an hour created a large amount of microscopic crystals that formed an emulsion-like mixture resembling thin paint. Can this process be inhibited?

By using 1000 ppm Ca++ (common ion effect) or 1000 ppm Mg++ (calcium carbonate crystallization inhibition) in tap water, turbidity can be reduced but not eliminated (see plot). Twenty percent isopropanol in tap water also diminishes turbidity to a similar extent.

E7C99E20-DD02-417B-8616-0B6AE437D052.png


To demonstrate that minimizing aragonite sand exposure is also beneficial for large scale sand washing, six kg of aragonite sand was washed eight times with ten liters of tap water each wash. I used a power drill equipped with a paint mixer to thoroughly mix the sand in a minimum amount of time. I discussed the power drill here


Mix time was 10 seconds. The trend in turbidity for the large scale washes was similar to that observed for the small scale pilot run (see plot).

2395E30E-2115-459A-A70C-3F3D3AF63D16.png


Samples of the wash water (photo below) show how turbidity caused by fines is quickly reduced and how persistently the wash water remains cloudy. Water is likely being wasted after the fourth wash.

6525DFB6-8584-41AC-951F-C2122AEDD9EF.jpeg
I’m certain I’ve missed a thread or something but why are we washing sand now? I’m not trying to be a wise butt either.
 

brandon429

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Because live sand marked

-No rinse required-


comes out like this in big reefs who prefer to start clean:



492D23BE-406F-43BD-A8EF-4CEF5E09F525.jpeg

pdxmonkeyboy


this entire sub industry wouldnt exist if caribsea would just keep their word.
 
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Dan_P

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I’m certain I’ve missed a thread or something but why are we washing sand now? I’m not trying to be a wise butt either.
No problem. New, aragonite sand is very dusty. You’ve seen the post from @brandon429 , live sand may just be new aragonite sand sprinkled with bacteria spores and labeled “live sand”. Also, in rip cleaning, where you remove a sand bed, rinse in tap water and return it to your system, you might try to rinse the sand until the rinse water is clear.
 

brandon429

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Wanted to make a distinction between new system preps and handling existing reef tanks: Rip cleaning a running reef is also for waste ejection and safety for tank moves, upgrades, invasion control

I find that a significant distinction vs startup rinses where we sought simple clarity from silt, it seems this study is restricted for startup rinse efficiency

we would need testing in other peoples systems to extrapolate findings here to all sand rinses

I would never have entrants into rip clean threads for living systems apply any partial rinse method or use the dissolution prevention steps since our target is waste ejection, I would consider it highly unsafe since no fifty page thread exists for partially rinsing 200+ living reef systems without killing 2%

tap rising for hours, the slogging wasteful mode, is the only documented safe method when dealing in live systems because we rinse out 100% of waste leaving no cloud gradients whatsoever

partially-rinsed living systems can die, have massive invasion outcomes, have mass fish kills (documented page one of our physical rinse thread) = true consequence that can only be found by handling the varied systems posted in work threads in my opinion

this method under review here I would not consider safe for someones running fifteen thousand dollar sps reef it would be highly experimental on their dime were it to be used for a tank move, transfer or upgrade between tanks.

tasked with handling a $15K sps reef I would strictly only ever use the old tap water way due to eight years of controlled outcomes logged, we need safety over efficiency in those cases
 
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Randy Holmes-Farley

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Seems like a pretty simple subject and not worthy of all this "science".

Reefkeepers range from those who want to understand the what and why of everything they do for a reef tank, and some just want a cookbook recipe, and many fall in between.
 

brandon429

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A way to test if this is simple and not in need of science review @mfinn

someone makes an open call thread titled: I will upgrade, move and fix invasions in any reef tank on the Internet without rip cleaning, then let people with $15K sps systems post up the jobs. From the couch on an iPad the author would tell them each step they’d take, no complete sand rinsing required, to not kill their setups and if one dies the writer is on the hook publicly for the outcome.


it would also test the science of sand handling by making that thread a set of rules, an order of ops, that anyone with a sandbed can follow without needing a customized transfer and handling plan

it would be an attempt to handle all the massive variation home to home that a mix of sand, silt and tank waste presents all handled by the few listed steps in the open call thread. Scary stuff I’m telling you… the risk of killing someone’s ten year running reef tank pride

tap water rinsing can provide that absolute safety, but it’s highly highly wasteful of water, inefficient, and takes eight hours prep per bag-we seek a better way equally as safe. As covered in other posts some people have bad and risky tap water, we want an alternate way of handling their tanks


this only seems like a waste of time from the initial evaluation, in the game proper there’s big cash on the line and big big risk for reef systems when handling sand within running reefs.

nobody has given a macna talk on skip cycle reef tank moves, transfers and upgrades to lock down the ideal procedure yet. Science of sand handling is still evolving


I’ve seen a couple thread articles written about tank transfers, using the authors tank as an example :)

But once we start collecting solely public jobs live time the subtle variables begin, that’s when the real fun and risk emerges to test any sand handling method.
 
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jda

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If the sand comes in water, then it probably can go straight into the tank, but it is probably not even close to live. If dry, then it is gonna be dusty. The only real live sand was shipped overnight from someplace in Florida and actually had worms, pods and other things in it when you opened up the bag.

You can use all of these without issue, or you can get into trouble with any of them. Details and nuance matter.

At some point, people have to stop believing a manufacturers, BRS (or the like), shills, video makers or other people who have skin in the game. It is on the hobbyist to be smart. Just like mining quarried terrestrial calcite, painting it with purple epoxy and spraying bacterial spores on it does not make the stuff live rock, you have to be smart about sand too.

I guess that new technology in sand could be coming (this was snark). However, it is not likely in our lifetimes.

I am a huge sand guy. I love it. I love what it does - completes the nitrogen cycle and buffers phosphate. I love the critters who live in it and what they do for my tank. I would use mixed grain size that can allow cucumbers to go to work - special grade reef sand mixed with some smaller sugar sized. I rinse it and then put it in - this takes like 5-10 minutes per bag if you know what you are doing. Once it gets some bacteria and film on it, it will stay put with power heads. After 3-6 months, it starts to chew through nitrates and house enough microfauna that any/most ich tomonts that land in there will be found for food. After a year, it is a non replaceable part of an ecosystem. I do like to clean it every 3-4 years and do small sections every few months with a gravel vac to get out the inert grey gunk that can gum it up.
 

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Not too long ago I made a claim about needing less water to wash new aragonite sand if you first sieve it to remove the fines.

https://www.reef2reef.com/threads/quit-wasting-water-washing-dry-aragonite-sand.953390/

Long story short, I was wrong. So, I went back to the lab to understand aragonite sand washing. Here is the new data that gives us insight into why aragonite sand is nearly impossible to rinse clean.

Everyone who has ever tried to wash aragonite sand until the wash water ran clear, faces performing what seems like an infinite number of washes. The orange line on the plot below shows how the cloudiness of the wash water (measured with the Hanna Color of Water Checker) declines rapidly at first but then refuses to budge much lower.

602CAC02-A9D1-4DBB-8BE0-51DC8CF64C8C.png


I initially thought that removing the fines by sieving the sand first would solve the problem of “infinite washes”. The blue line in the above plot shows it does not help. What is going on?

One of the first hints about what is happening during aragonite sand washing came from comparing data from two sand washing experiments. By overlaying the turbidity data from washing 100 mL and 200 mL of sand, the process looks like it might involve two stages. The first stage is where the turbidity is correlated with the initial sand mass while the second stage seems to occur with little or no difference between the two initial sand masses. The correlation of the first stage turbidity with the initial sand mass suggests turbidity is relates to the amount of fines suspended in the wash water, while the second stage turbidity, seemingly unrelated to the amount of sand present, means what?

55D7BEE0-C604-4201-8451-4729A4EC6EBF.png


To investigate the process in the second stage further and determine whether it occurs throughout the entire sand washing exercise, the turbidity of the wash water was measured, then it was filtered through a 1.6 micron glass filter to remove the fines. Each filter was weighed before use and then again after filtration and drying. Turbidity of the filtrate was also measured to assess how much turbidity there was that was not associated with the fines in the sand. Comparing the turbidities of the wash water and filtrate (see plot) demonstrates that the second turbidity generating process occurs in every wash.

B330436F-B6CE-43AF-89EF-5EB828AF8429.png


Comparing turbidities of the filtrate against the wash water turbidity minus the filtrate turbidity indicates that the decline in turbidity caused by fines might be faster (orange line) than the decline in turbidity caused by the second stage process (blue line).

F5EFD846-BC1C-492D-82C1-0A8D4CBFABA1.png


With regards to the mass of the filtered fines, it is well correlated to the turbidity of the wash water (see plot). The intercept is not zero pribably because of the turbidity caused by stage two turbidity.

57A9BD40-4057-477F-8925-4B179942D838.png


Data that gave me a hint about what might be happening in the second turbidity generating process involved stirring washed sand in tap water for varying lengths of time (see plot below). This data makes clear that wash water turbidity rapidly increases with the time that sand is exposed to tap water. Interestingly, stirring aragonite sand for one hour in tap water resulted in wash water resembling a thin, translucent white paint. This last observation suggests that a crystallization or precipitation is occurring. But why?

8809F309-1F85-49D8-AE9C-676F8B64F479.png


The sand used in the experiments contains aragonite, a form of calcium carbonate. Calcium carbonate has two major polymorphs or crystal forms, aragonite and calcite. Aragonite is typically formed by living organisms and is less stable than calcite, just like diamond is less stable than graphite. A manifestation of calcite stability is its lower solubility in water compared to aragonite. The consequence is that when aragonite dissolves in water (calcium carbonate is slightly soluble in freshwater), the concentration of calcium carbonate exceeds the solubility limit of calcite and crystals form. This dissolution-crystallization process can continue as long as there is aragonite present because crystallization continually removes calcium carbonate from solution, allowing more aragonite to dissolve. Stirring aragonite sand for an hour created a large amount of microscopic crystals that formed an emulsion-like mixture resembling thin paint. Can this process be inhibited?

By using 1000 ppm Ca++ (common ion effect) or 1000 ppm Mg++ (calcium carbonate crystallization inhibition) in tap water, turbidity can be reduced but not eliminated (see plot). Twenty percent isopropanol in tap water also diminishes turbidity to a similar extent.

E7C99E20-DD02-417B-8616-0B6AE437D052.png


To demonstrate that minimizing aragonite sand exposure is also beneficial for large scale sand washing, six kg of aragonite sand was washed eight times with ten liters of tap water each wash. I used a power drill equipped with a paint mixer to thoroughly mix the sand in a minimum amount of time. I discussed the power drill here


Mix time was 10 seconds. The trend in turbidity for the large scale washes was similar to that observed for the small scale pilot run (see plot).

2395E30E-2115-459A-A70C-3F3D3AF63D16.png


Samples of the wash water (photo below) show how turbidity caused by fines is quickly reduced and how persistently the wash water remains cloudy. Water is likely being wasted after the fourth wash.

6525DFB6-8584-41AC-951F-C2122AEDD9EF.jpeg
Going on 5 years now. No water changes and straight well water. No filter, no sand washing, no water changes. Lots of aquarium maintenance is not necessary. Tanks can be kept as simple as possible. Eventually these particles will settle into the sand bed.
 

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brandon429

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that applies only to a reef sitting in a home, a very nice one


but what if someone’s costly reef had a required action phase, such as a rescue from a Red Sea split seal tank owner.


what would you do if eighty people emailed you about how to move the reef to another city, or do a full transfer install of an existing tank while they video and picture it live time for all the aquarium world to see



would you still not rinse


and if not, what thread or resource did you get the non rinse procedure from
 

WilGao

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Even seeing the data before, I'm still a little gobsmacked that the cloudiness that never ends is because we are dissolving the sand with every rinse.
So @Dan_P continuing my line of dumb questions, how would you rate these three solutions that hobbyists might easily have - in terms of preventing dissolution of aragonite sand?

1) tank water

2) Kalkwasser, saturated Calcium Hydroxide

3) Saturated sodium bicarbonate baking soda
I agree, it's more about erosion.
 
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Dan_P

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I agree, it's more about erosion.
Unlikely erosion because the sand grains are just not moving fast enough to bump into and break other sand grains or remove a jagged edges. I got first hand experience about the hardness of aragonite sand by grinding it in a mortar and pestle. This stuff is like a rock :)
 

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