[Poseidon]

Here is the sand I plan on using when I move the tank in Feb.

Link

[Ninong]

Originally Posted by Poseidon

Here is the sand I plan on using when I move the tank in Feb.

Link

Why do you want to use calcite instead of aragonite?

Do you realize that the particle size of that product ranges from 1mm - 5mm? That's extremely large!

What is the source of their product?

Why are they using deceptive advertising, such as trying to make people believe that their calcite is "magnesian calcite" (obviously a typo) and therefore somehow superior to "ordinary calcite." All calcite is magnesium calcite. It is either low-magnesium calcite or high-magnesium calcite. Low-magnesium calcite is CaCO3 that contains less than 4% MgCO3. High-magnesium calcite is CaCO3 that contains more than 4% MgCO3.

From their website:
Q: Will Gray Coast buffer the water and dissolve into calcium like sugar size aragonite?
A: Calcite, like aragonite, crushed coral, and dolomite, are all forms of calcium carbonate. They just exist in a different crystalline formations and have different levels of dissolvability. Our Calcite, of all the above mentioned materials, has an incredible magnesium content. It is actually a magnesium calcite and has a somewhat higher buffer capacity than aragonite.

Notice that this statement is basically meaningless. First of all, what exactly is "an incredible magnesium content?" What exactly does that mean? What is the magnesium content? And after acknowledging that the different crystalline forms of CaCO3 have different levels of dissolvability they said nothing about the fact that calcite does not dissolve as readily as aragonite. Isn't that important?

All calcite requires a lower pH to dissolve than aragonite. Neither aragonite nor calcite will dissolve at normal marine aquarium pH levels. However, aragonite will begin to dissolve at a pH of 7.7 or less. Calcite doesn't begin to dissolve until the pH is considerably lower than that.

I'm not going to get into a discussion of exactly how much true net dissolution of aragonite you can get in a DSB because I lost that argument a long time ago and gave up on it. It was pointed out to me that all of the discussions in favor of dissolution of aragonite in a DSB failed to take reprecipitation into account. Regardless of how much net dissolution you think you get with aragonite, you will get less with calcite.

This is the same company that still sells Al2O3 (aluminum tioxide, aka alumina) as a phosphate sponge even though most of their competitors have discontinued this practice and the same company that adds extra boron to their salt. (P.S. -- Go to their website and click on reef salt ion composition. Notice the 16 ppm Boron, which is 4 times NSW levels and much higher than any other salt.)

Besides, the color is just awful!



P.S. -- Looks like they offer regular aragonite, too. That's the only product that they tell you the particle size of in the ad copy (0.25-0.50mm), which I guess amounts to a fairly large sugar size.

[Poseidon]

George, thanks for the critique. I know SeaChem has some swful products, especially the phosphate remover, followed closely by their salt, I would never use either of them.

However, this is the table where they list the chemical makeup:

Calcium

197,500

Cobalt

4

Iron

2876

Potassium

417

Magnesium

115400

Manganese

43

Molybdenum

6

Strontium

63

Vanadium

7

Zinc

23

You can see that this gravel has a rather HIGH magnesium content, which according to Calfo, has allowed him to quit dosing a Mg supplement at all. As it stands my Mg content is pretty stable, but this is just one more way I can/may be able to eliminate a supplement.

The size of the gravel is large, but with the results of the DSB study showing the effectiveness of the sand is for the most part NOT dependant on grain size. Also I am counting on the larger grain size to help eliminate "sand storms" Maybe I will be able to increase my overall flow without blowing so much sand around.

Lastly, the color.... I like it! I am hoping that I will be able to use that to my advantage as well. Maybe because I am a photographer, but the dark gravel will open up some interesting lighting opportunities for me! I am also hoping it will help with contrast, my BRIGHT purples, and greens contrasting greatly with the dark substrate, rather then competing in brightness with a white sandbed.

As for the color, I like it! I have seen it

[Poseidon]

Doh.... My table that I copy/pasted looked so much better while I was typing, now the numbers are skewed....

Oh well....

[Ninong]

Originally Posted by Poseidon

The size of the gravel is large, but with the results of the DSB study showing the effectiveness of the sand is for the most part NOT dependant on grain size.

A DSB performs other functions in addition to denitrification and smaller particle sediments are more conducive to those other functions because they harbor a more diverse array of infauna.

Where are they getting this stuff?

[Poseidon]

You are correct, the smaller grain size is better for some life. My DSB seems to be pretty sparse anyway lately as far as worms, stars, snails, etc.... I do have some cool "baby" brittle stars though....

As for where SeaChem is getting it, I don't know. Maybe I will give them a jingle!

Well I called, Tech Support wasn't very helpful. When I suggested that I use the Forum to ask my questions, Rashida was all for it! I think she appreciated that I offered her a way off the hook, as she could not answer my questions.

Here is a link to my thread over there.... Maybe you can help me decide George, if you wish to participate, or if you are just trying to protect me from myself that is cool too!

[Mr.Firemouth]

Calcite is calcite like he says.
I use it post calcium reactor output for magnesium replacement in home made reactor. The low pH effluent will actually allow product to work.
The ad is misleading. Magnesium levels are up to 1500ppm

[Ninong]

Originally Posted by Poseidon

You are correct, the smaller grain size is better for some life. My DSB seems to be pretty sparse anyway lately as far as worms, stars, snails, etc.... I do have some cool "baby" brittle stars though....

As for where SeaChem is getting it, I don't know. Maybe I will give them a jingle!

Well I called, Tech Support wasn't very helpful. When I suggested that I use the Forum to ask my questions, Rashida was all for it! I think she appreciated that I offered her a way off the hook, as she could not answer my questions.

Here is a link to my thread over there.... Maybe you can help me decide George, if you wish to participate, or if you are just trying to protect me from myself that is cool too!

Let's take a look at the answer their Tech Support person gave you:

We do not disclose any propietary information regarding the source or origin of our gravels such as Gray Coast. Nevertheless we are more than happy to provide information regarding the nature of magnesium calcite which is the main composition of Gray Coast. (See Index of /products/product_pages GrayCoast.html)

Magnesium calcite is known to be less soluble than aragonite;

[Yes, we already talked about this. Aragonite is less stable than calcite. Aragonite begins to dissolve at a higher pH than calcite. Therefore, aragonite is a preferred sand for anyone interested in using it for it's reputed buffering properties.]

...consequentially magnesium calcite has a lower pH in which it begins to buffer than aragonite which buffers at around a pH of 7.9.

[I believe the correct number is a pH of 7.7 for aragonite, not 7.9]

Magnesium calcite begins to buffer the water at a pH between 7.5 and 7.7, depending on concentration and temperature; see article on magnesium calcite at http://www.minsocam.org/ammin/AM76/AM76_1889.pdf.

[I believe a more accurate number is a pH of 7.4 for calcite. Perhaps they are stretching this to benefit their marketing claims? His link is broken so I can't check out that article to see what concentration and temperature they're talking about that would cause calcite to dissolve at 7.7 pH.]

Unlike other calcites such as low magnesium calcite and aragonite,

[Other calcites such as aragonite makes no sense. By definition, aragonite is not calcite. Calcite is calcite and aragonite is aragonite. They are both CaCO3 but their crystalline structures are different.]

...high magnesium calcite as found in Gray Coast increases considerably Mg concentration in saltwater.

[Only if it dissolves. It might be more useful in a calcium carbonate-carbon dioxide reactor where the lowered pH from the CO2 would cause it to dissolve.]

The increased magnesium concentration will only help to stabilize the pH in saltwater and not lower it to 7.5.

[I have no idea why he thought it necessary to point that out but maybe he thought you wouldn't understand???]

Additionally, magnesium makes calcium more soluble. A higher magnesium level in solution keeps more calcium in solution rather than binding to carbonate to form calcium carbonate (i.e. white chalk forming in an aquarium). In theory, the right concentration and ratio of magnesium and calcium in solution equates to more calcium and magnesium readily available to corals and fishes.

[All he is saying here is that you should maintain Mg at NSW concentration of ~1300 ppm. We all know this already. If your Mg drops much below 1000 ppm, you will have problems maintaining proper calcium and alkalinity levels.]

Additionally, there is no cause for concern regarding the increased level of magnesium that will be maintained in solution in a saltwater tank from the Gray Coast. In fact the Gray Coast will actually prevent your saltwater from becoming magnesium deficient by providing a steady supply of magnesium to your aquarium.

[The steady supply of Mg depends on the calcite readily dissolving. As you know, some people say that even aragonite doesn't dissolve enough to make a significant contribution to buffering. I used to think it did but I'm not so sure about that anymore. I now tend to think that the buffering potential is overstated. And that's for aragonite, which dissolves much more readily than calcite.]

As for the Gray Coast's suitability for sand-dwelling creatures in your saltwater aquarium, Gray Coast is not too coarse for aquarium use. Generally Gray Coast has a grain size ranging from fine sand to 1 mm, up to 5 mm. The finer sand will settle to the bottom for sand dwellers and the fewer, larger bits will remain scattered at the surface.

[It's far from ideal for any number of sand dwelling creatures and definitely not a good choice for fish that like to sift throught the sand or bury themselves in the sand. He's right about one thing though -- the finer particles will all settle to the bottom and you will end up with large particle gravel on top.]

[Poseidon]

Thanks George.

I guess it does come down to marketing, I'll bet mixing this product in a reactor like you say would be the most effective use of this product. Since I use a Kalk reactor, it looks like I am going to be crossing this one off my list. I may still consider it, just for color alone though, and then only as a SSB rather then a DSB....

[Ixthys]

Do to my supernatural computer abilities, I have fixed the link.

BEHOLD MY MAGIC!!!

http://www.minsocam.org/ammin/AM76/AM76_1889.pdf

[Ninong]

Originally Posted by Ixthys

Do to my supernatural computer abilities, I have fixed the link.

BEHOLD MY MAGIC!!!

http://www.minsocam.org/ammin/AM76/AM76_1889.pdf

Thanks!

[Ninong]

Originally Posted by Poseidon

Thanks George.

I guess it does come down to marketing, I'll bet mixing this product in a reactor like you say would be the most effective use of this product. Since I use a Kalk reactor, it looks like I am going to be crossing this one off my list. I may still consider it, just for color alone though, and then only as a SSB rather then a DSB....

The article they linked concerned the dissolution of synthetic magnesian calcite. The pH values of 7.5 to 7.7 for synthetic magnesian calcite varied for the temperatures they tested.

The only pH values that I am familiar with are for biogenically produced calcite and aragonite. That's where I got the figure of 7.7 pH for aragonite and 7.4 pH for calcite. I wasn't thinking of very high-magnesium synthetic calcite. Aragonite, calcite and vaterite are the three polymorphs of calcium carbonate. Their differing physical properties are due to differing crystalline structures of CaCO3.

So I don't know what to tell you about it other than I don't find it all that appealing personally. I wonder why Anthony Calfo decided to try it? You might ask him if it's synthetic or biogenic calcite. I suspect it's synthetic. I have no idea if that really matters but I suspect it's synthetic. I wonder if this is something they use in the cement/concrete business???

You could always post another question over on the manufacturer's board: "Is this biogenic or synthetic magnesian calcite?" They will probably tell you that is proprietary information.

[Poseidon]

Ixthys, thanks for helping with the link.

George, thanks for the "cliff notes" version, my head is still not "in the game" due to the tough week in the hospital...

[CSeaSee]

Hi guys-
I'm not going to jump into the chemical arguments here (because I've heard this all before), just offer some anecdotal observations. I put that substrate into my 10 gallon acrylic tank- originally for a mantis shrimp, still haven't found one around here- and the tank has been fine- there aren't and sps/lps in there, but there were a couple of corallimorpharians in there for a while when my 55 crashed and they survived just fine- I haven't had any large problems maintaining the pH, etc, although the tank is used as QT right now. The color is great, and the grain size is actually quite small.