View Full Version : How to make calcium sand?

07/05/2017, 10:01 PM
Ok. I realize that this is an unusual approach, but what if...

instead of buying aragonite sand at $1/lb, is it possible to make it for less.

The basic idea is to make a CaCl2 mix and NaHCO3 mix using off the shelf chemicals at a hardware store (or bulk sources), then combine then to make CaCO3 and salt.. collect the precipitate and that's the sand - maybe I can recycle the salt too and just add the missing elements (with Fritz maybe).

Why? I need a ton = 2000lbs... so, I could have it trucked in for $2-$3K, or look for alternatives. I may actually need more, but that's the starting point.

First, I'm wondering if there's an easier chemical process to making it? Less complicated maybe?

I'm also not sure how (or if it's possible) to achieve a particular grain size. Maybe a sieve that screens the media regularly to collect the sand that's grown to the right size...

I can get a pallet of 2500lbs of CaCl2 for $1600... I may be able to get it for less.. I just need the cheapest chemistry to make it into sand. I can get baking soda for $0.50 per pound (so far).

Saving $1000 is worth it to me, even if it takes longer and takes some effort.

07/06/2017, 07:10 AM
I haven't tried it, but I can't see making your own sand working out very well. Even if the process works, there's no efficient way of getting remotely consistent grain size. I imagine the precipitate would be mostly a fine dust, which is of course useless. Even thinking your could sift out any good sized grains, there would be a lot of waste in grains that are not large, which would add to your raw material cost as your yield will not be even close to 100%. I feel like you'd easily spend hundreds of dallars or more trying to get some sort of setup that might work. Not worth the risk IMO.

If you think you have a good method though, it's easy enough to take a pound of baking soda and add it to your Calcium chloride and see what you need to do to get useful sand out of the mixture. If this works small scale (5 gallon bucket) than you'll have an idea of how difficult/feasible it is large scale.

You can also check craigslist for people that may be selling large quantities of sand that you can buy locally, and clean yourself instead of making yourself. That's the route I think I'd take if I needed a ton of sand.

07/06/2017, 09:45 AM
I looked and I can get cheap silica, not cheap Calcium sand.

$1 per pound is the best I can find.

Would heating accelerate crystal growth?

How about adding CO2?

Is there an additive that would control crystal size?

This is the chemistry forum... you're the experts.

07/06/2017, 04:28 PM
So your cost for calcium (sans chloride) is about about $1.77, and carbonate is running around $0.70 a pound, which comes to $1.13 for the ingredients.

Heating would increase the precipitation rate. Carbon dioxide would slow it. I can't think of anything to control crystal size. You might need to add some sort of mechanical sifter to remove crystals from the mix when they get to your desired size. This could be a fun project to try for entertainment, but I suspect that it'd be more cost-effective to have aragonite sand shipped to Texas.

Darrell Brady
07/06/2017, 04:33 PM
take a few trips to the beach.

07/06/2017, 05:22 PM
A ton is a lot of trips.

Is there a cheaper way to convert CaCl2 to CaCO3?

07/06/2017, 06:09 PM
You could consider pricing some bulk calcium oxide or calcium hydroxide, but I suspect you'd just end up with very, very fine fluff. There are natural aragonite sand deposition processes that happen in the ocean, if my memory is correct, but I think you'd have a hard time duplicating them at home.

07/06/2017, 11:49 PM
A ton is a lot of trips.

Is there a cheaper way to convert CaCl2 to CaCO3?

While both are forms of calcium carbonate, they're not the same. The sand you want is aragonite. What you will get when you mix CaCl2 and Na2CO3 is chalk.

07/07/2017, 12:48 AM
ok. so is there a way to make aragonite?

07/07/2017, 11:34 AM
Not really, the precipitate will likely not coaless into large particles, rather it will precipitate as very fine dust or chalk as disk1 mentioned. There's no mechanism for these fine particles to merge together to form larger ones like sand. If this was the case, sand particles would merge with each other and the ocean floor would just be one big rock.

07/07/2017, 11:42 AM
ok. so is there a way to make aragonite?

Grow stony coral, add parrot fish and wait? This may not meet your desired timeline.

07/07/2017, 02:05 PM
Sand is formed from weathering rocks. Aragonite sand comes from coralline algae and pulverizered coral.

Precipitation usually produces very fine particles, a silty material that would look like mud when you tried to filter it. Centrifugation might be the only way to isolate it. Curing the silt, see Oswald ripening, might be the way to get bigger particles or at least agglomerates that could be filtered, but particle is still very small.

Mixing CaCl2 with sodium carbonate would likely form calcite not aragonite, so, thermodynamics is against you.

Processing a ton of materieal would require a small pilot plant. That is going to drive up the price.

So, the answer is that processing a ton of material is very likely over your budget and probably far from your equipment capability.

If you absolutely need aragonite sand, buy it, although I have to wonder why silica sand is not an option.

07/07/2017, 04:35 PM
I'm not sure why you would specifically need aragonite version of CaCO3, but one of the most common sources of calcite rock is marble. White marble specifically contains few impurities and if you can find a source of scraps of white marble, then this can be ground into nice gravel with basically the same chemical properties as aragonite sand. The whole reaction you described would produce a fine dust of chalk, and only then you could coalesce it into grains somehow.

07/07/2017, 09:31 PM
crystals would grow if left in a super-saturated solution of the ions that create that crystal.
here's salt crystals coming out of a natural supersaturated solution in the dead sea


that was the idea - but chalk isn't useful

silica sand doesn't buffer the tank and some silica can scratch or kill some organisms and potentially promote diatoms.

ok - if the experts can't do it, then I'll have to buy a palette or two.

07/08/2017, 05:59 PM
I agree that it's possible to grow crystals, but I don't think it's going to be very easy to do with calcium carbonate. It's an interesting idea. You could try it at small scale to see how practical it might be. It might be a fun project, whatever the result.

07/08/2017, 07:29 PM
Growing crystals of salts with very low solubility is next to impossible but quite easy with readily soluble salts. So, good move on shelving the idea.

The notion that aragonite sand buffers water sounds plausible but it is unlikely to be important. As far as I can tell, bare bottom aquariums do not have buffering issues. On the other hand, systems with aragonite still need calcium and alkalinity additions. I can't find a head to head experiment between silica sand and aragonite that shows aragonite has a significant effect on maintaining alkalinity or calcium levels.

The increase chance of diatom growth is likely to be a "better safe than sorry" notion rather a scientific fact. Again, I cannot find a head to head study the shows silica sand is more likely to promote diatom growth.

Silica sand scratches or kills some organisms sounds plausible but never heard that this was an important concern. Maybe silica sand is a bit heavier than aragonite sand, but does it matter? I will keep an open mind until I track down the facts.

Two reasons to avoid aragonite is because it adsorbs phosphate and organics to a much higher degree than silica sand and it is a reactive solid, becoming cemented into a block. I understand it is a standard substrate and many aquarists use it successfully, but as fair as expense and opportunities for maintenance problems, silica sand seems the better choice for a substrate.

Anyway, great question.


07/08/2017, 07:39 PM
A lot of people have run very successful tanks with silica-based sand. I personally don't like the look of the ones I've seen, at least close up to the tank, but they should work well. Silica will scratch glass a bit more readily than calcium carbonate in most of its forms, although the difference seems to be fairly small in practice.

07/08/2017, 08:30 PM
The grain size and shape is critical for benthic life, particularly worms. My aragonite sand beds have always shrunk over time in my tanks. As have any shells I've added. I had two large queen conch shells and two large clam shells that have substantially shrunk and gotten thinner over the last couple of years.

Do they release phosphate? Great! In my setup, it only feeds more life and growth.

07/09/2017, 07:27 PM
If coral rubbles are cheaper, it will be much easier to grind it into a suitable size you fond off.

07/09/2017, 08:41 PM
Crushing rock usually creates sharp edges vs natural weathering with rounded edges. Also- don't have a grinder. Also haven't checked the cost of a ton of coral rubble.

Would crushed oysters or egg shells work?

07/10/2017, 07:25 AM
Makes me wonder what is the appropriate binder that could be used to agglomerate precipitated CaCO3, I have several tons of that (food grade) material. Pan or drum granulation would produce nice rounded granules.
Interesting question!

07/10/2017, 07:41 AM
Hmmm... so why do you have several tons? :)

Do you have drum granulation equipment? Does the binder stay after the spheres form? What happens after the Calcium chalk dissolves?

Maybe I should start with chalk powder : 2000lbs @ $1500


Not a great deal

07/10/2017, 08:10 AM
just get a Hawaiian parrot fish and feed it a lot, it will poop out sand! white sand! lol

07/10/2017, 08:15 AM
Is this real.. $250 for a ton (+shipping?)



This one has no price...


Maybe I don't need to make it after all...

07/10/2017, 11:24 AM
Seems legit to me, but be prepared for the shipping costs to be more than the sand. I recently bought a 250 gallon tote for ~$250 and the shipping ended up being a bit more than the toe because it was large. Certainly shipping something that weighs 2,000 pounds will be pricy. Just call and get a shipping quote and lead time and see if it fits your needs. Note that it does seem like sand that has "free silica" removed from it, but still would have bound silica which could possibly be released over time with wearing down? Not sure on that one.

07/10/2017, 11:40 AM
I usually ask for a baggie to test. I drop it in a cup of vinegar... it it fizzes, it's good.

This time, I'll weigh it before and after. See the non-Calcium content by weight

07/10/2017, 04:20 PM
Those look like legitimate products to me, but the shipping might be very pricey. The comments on silica are a bit iffy, but I agree with them that there's likely to be a bit of silicate in most every type of sand. It'd be interesting to know the percentage for their products.

07/11/2017, 07:56 AM
Would be nice to have an idea of the grain size as well. Too small of a grain will cause your sand to blow all over with your powerheads, and cause the sand to look more like sand dunes. May be tough info to find though. I worry a bit because they say it's the softest sand, which to me means small grain size.

07/11/2017, 06:07 PM
That's another good point. I would want to check it in person or get some idea of the size before spending a lot of money.

07/13/2017, 03:15 PM
Realreefrock quoted $1650 for a pallet delivered. Still confirming if a pallet is 2000lbs.

Still. The idea of small spherical balls of calcium carbonate is very interesting.