Dolomite as a substrate?

[mrbncal]

In my search for a suitable alternative for Carib Sea's product I have found a 50 pound bag of "dolowhite". It says on the bag that it is a natural white dolomite and is made by chemicalime.
I put a tablespoon of the sand in a cup with a cple tblspns of vinegar and it fizzes.
If you rub some really hard between your thumb and fingers you can get it to break up a little smaller. Its tough but you can.
It has a little shine to it and its sized a little smaller than Caribseas special reef grade. Oh and its BRIGHT white.
Hailing from northern california and never having seen southdown type sand I cant give comparisons, but it is not a smooth sand. Definately has sharp sides and points.
Question is would this be alright as a safe alternative for a 1/2 - 1" shallow sandbed in a mostly sps 75 gallon reef?

 

[Ninong]

Re: Dolomite as a substrate?

<a href=showthread.php?s=&postid=9496252#post9496252 target=_blank>Originally posted</a> by mrbncal

I put a tablespoon of the sand in a cup with a cple tblspns of vinegar and it fizzes.

Of course it fizzes, but not as strongly as aragonite. This test assumes that you are trying to determine if a white sand is really aragonite or just a whitish quartz sand. If you know it's dolomite, there's no reason to test it.
Dolomite is CaMg(CO3)2, calcium magnesium carbonate. Aragonite is CaCO3, calcium carbonate. Both will react with acid to produce carbon dioxide.

I would pass on the dolomite myself.

 

[mrbncal]

Yeah I know, I just wanted to do it so the kids could see it fizz and thought it was cool dont know why I mentioned it other than I figured someone would ask anyway, now...

wouldn't the additional magnesium be beneficial? So it doesn't break down(buffer) as well as aragonite, is that the only reason not to use it?

Its only $7 for 50 lbs.

Elaborate on why you would pass please.

 

[frank2926]

Lots of people run it in a calcium reactor, other than being sharp I dont see a reason to not use it. Dolamite was used for years in fresh water setups for a substrate. I am not sure but I dont think it breaks down as quickly as argonite either. Running it in my reactor for 2years and when the arogonite is near exhausted I can still clearly see the dolamite.

 

[Ninong]

<a href=showthread.php?s=&postid=9497743#post9497743 target=_blank>Originally posted</a> by mrbncal
Elaborate on why you would pass please.

I would pass on dolomite as a substrate because Dr. Randy Holmes-Farley said that he would not use it as a substrate and that's good enough for me.

Here is what Randy posted when asked if dolomite was an acceptable choice for a substrate:

It will do nothing added to a tank as it likely will not dissolve. I would not use it as a substrate in a tank. If you put some in a CaCO3/CO2 reactor, it may be useful for maintaining (not raising) magnesium.

I discuss dolomite here:

Magnesium in Reef Aquaria
http://www.advancedaquarist.com/issues/oct2003/chem.htm

from it:

"It has been suggested that adding dolomite to CaCO3/CO2 reactors can help with magnesium problems. Dolomite is a material that contains both magnesium and calcium carbonate. If dolomite is being added to the reactor to maintain existing appropriate magnesium levels against the continual depletion via calcification (for example, if the calcium carbonate being used is too low in magnesium to maintain adequate magnesium) then this is a fine approach.

However, this method is unsuitable if the goal is to raise magnesium levels. The problem is that for every magnesium ion released from the dolomite, 2 units of alkalinity are also released:

MgCO3 ---> Mg++ + CO3--

Consequently, if one wants to raise magnesium by 100 ppm, the alkalinity will necessarily rise by 8.2 meq/L (23 dKH). The only way around this problem is to add a mineral acid (not vinegar) to the aquarium to reduce the alkalinity, and that may be more problematic than just adding magnesium in the first place."

 

[mrbncal]

Well I'm not using it to raise Mg. Just seems better to use this than playsand. Of course the best choice would be an aragonite of some sort, but not for a dollar and change per pound. I'll find some aragonite on sale and put a 15 pound bag in a bucket for a RDSB to help buffer.

 

[Ninong]

<a href=showthread.php?s=&postid=9500771#post9500771 target=_blank>Originally posted</a> by mrbncal
Well I'm not using it to raise Mg. Just seems better to use this than playsand.

No, I think playsand would be much better than dolomite, even regular quartz play sand. I would prefer aragonite play sand myself but if forced to choose between dolomite and regular quartz play sand, I would choose the regular quartz play sand because of the particle size.

 

[mrbncal]

Hmmmm, well the only playsand we have available here has a lot of dark grains in it. Not the look I was going for.

Thanks for all the replies folks.

Starboard threads here I come.

 

[Icefire]

Dolomite is okay and won't scratch the glass as quartz would do.

 

[mrbncal]

Thanks for the reply, funny I was just browsing a Canadian forum and they have some great info on dolomite as a sand bed, some of it referenced from RC. I think the general concern is lack of buffering capacity compared to aragonite and possible release of to much magnesium. They even have a thread about dolomite as a threat in DSB the discussion added by Randy Holmes-Farley where he states that dolomite is not harmful. But if the ph stays where it should than the release is minimal and I had planned on using a remote deep sand bed like Anthony Calfo describes in one of his posts to deal with nitrates and aid in buffering capacity. Much cheaper to do it this way.
Also the dolomite has that great bright white color. Besides I am only using a 3/4-1" bed in the display. And that is the only place this will be used.

*by the way ninong the last paragragh of the link you provided seems to point to the importance of having magnesium in the reef tank. and I have yet to find the post that you said the good doctor tells why dolomite is not a good choice. A little help please

 

[Ninong]

<a href=showthread.php?s=&postid=9506955#post9506955 target=_blank>Originally posted</a> by mrbncal


*by the way ninong the last paragragh of the link you provided seems to point to the importance of having magnesium in the reef tank. and I have yet to find the post that you said the good doctor tells why dolomite is not a good choice. A little help please

The link was included in Randy's post that I copied for you. I copied his complete reply from a thread last year.

If you go back and read by post again, this is what I said:

I would pass on dolomite as a substrate because Dr. Randy Holmes-Farley said that he would not use it as a substrate and that's good enough for me.

Here is what Randy posted when asked if dolomite was an acceptable choice for a substrate:

It will do nothing added to a tank as it likely will not dissolve. I would not use it as a substrate in a tank.

In my very first reply in this thread, this is the advice I offered: I would pass on the dolomite myself.

In all of my replies, I made it clear that I would not use it. That should not be taken as a prohibition against anyone else using it if they so choose. My attitude towards dolomite is not based on any "harm" that it might do because I don't believe it will dissolve at anything near normal reef aquarium pH but rather based on the particle size compared to Oldcastle/Southdown aragonite sand or Carib-Sea's sugar sized aragonite sand. The particle size of the substrate is an important consideration for those wishing to provide a suitable habitat for a diverse community of sand bed infauna and epifauna.



P.S. -- I have no idea why Dr. Randy Holmes-Farley posted that he would not use dolomite as a substrate but the fact that he did post that on more than one occasion may have influenced my thinking on it because I remembered that Randy had rejected it as a substrate. In truth, I myself have never considered it as a possible option for a substrate but others have raised the question from time to time and my usual response is that I wouldn't use it and neither would Randy.

 

[mrbncal]

Ninong, hope your not defensive as I am not attacking or challenging your views in any way. I'm just looking for peoples views. If you dont like dolomite thats fine, I was just looking for explanations or research. I have never dealt with dolomite and I was looking for pros and cons.

So far it seems like a nice alternative to the bare bottom look. If I do some gravel stirring and routine maintenance on it I think I could use it. I dont really care if it buffers or not, its just for aesthetics.

I want to follow the basic philosophies of BB tanks (hi flow , good skimming and lo nutrients) but modify it just enough to suit me

 

[Frick-n-Frags]

Know your players. IMO just ignore him..

It is totally a particle size issue.
I think the size will make for an easy fouling, and for sure a nitrate factory if used as a full substrate.

dolomite quickly "skins" over and becomes essentially inert regarding any kind of buffering effects. Never was worth a crap, even in the dolomite-driptray dark ages, for buffering.

I agree, a sprinkle to cover the glass would be fine and you could actually vacuum that to get the crap out of it, thus maintaining the BB concept as you mention.

But bottom line: it won't hurt anything along with not doing anything chemisty-wise

 

[Amphiprion]

<a href=showthread.php?s=&postid=9512041#post9512041 target=_blank>Originally posted</a> by Frick-n-Frags
Know your players. IMO just ignore him..

It is totally a particle size issue.
I think the size will make for an easy fouling, and for sure a nitrate factory if used as a full substrate.

dolomite quickly "skins" over and becomes essentially inert regarding any kind of buffering effects. Never was worth a crap, even in the dolomite-driptray dark ages, for buffering.

I agree, a sprinkle to cover the glass would be fine and you could actually vacuum that to get the crap out of it, thus maintaining the BB concept as you mention.

But bottom line: it won't hurt anything along with not doing anything chemisty-wise

I agree on the particle size. Buffering capacity of substrates is of minimal concern in most cases. Even aragonitic sand contributes very little, especially when coated with a biofilm. So there is essentially very little difference between quartz sand and aragonitic sand in that regard. I would shy away from dolomite just due to the grain size and the maintenance associated with it.

 

[mrbncal]

Just to clarify, the size of the dolomite product I have is in between the carib sea special reef grade and the fine sand in the sand blasting size.
It falls into the oolitic sand size according to particle size but the edges are sharp.
I appreciate all your replies folks.

 

[Darsh85]

I know some people don't like resurrecting old posts, but I do haha.
Has something changed in the last 10 years regarding aragonite's buffering? Here it says aragonite contributes very little and only a little more than dolomite?

 

[cody6766]

I don't have much to add, except that Bender is 40% dolomite.