Does adding Sand cause a drop in Alk.?
- Thread starter bgdiving
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randy holmes-farley
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- Arlington, MA
Yes, adding calcium carbonate sand can lower alkalinity. Tank water is supersaturated with calcium carbonate, and the fresh sand acts as a nucleating agent to trigger precipitation of CaCO3. You can also see the pH drop for the same reason if you add enough sand.
Thanks Randy, Would this be a one time event? or could it continue to cause alkalinity to drop untill biofouling accurred? I assume biofouling would start to show up in 3 to 4 days but could alkalinity continue to drop after that point until the sand particles are totally biocoated?
Would adding sodium bicarbinate raise alkalinity or just cause more calicium carbinate to percipitae out?
Would adding sodium bicarbinate raise alkalinity or just cause more calicium carbinate to percipitae out?
randy holmes-farley
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- Location
- Arlington, MA
DK:
<< Randy, Wouldn't that be a tempory effect with a longer term (hoursor/days)with a slight increase in alk? >>
The drop is, IMO, permanent until you add more alkalinity somehow. The ability of the sand to cause a drop is temporary. It lasts only a short time until enough magnesium/phosphate/organics get onto the surface and inhibit further precipitation of CaCO3.
bgdiving:
<< Thanks Randy, Would this be a one time event? or could it continue to cause alkalinity to drop untill biofouling accurred? I assume biofouling would start to show up in 3 to 4 days but could alkalinity continue to drop after that point until the sand particles are totally biocoated?>>
It seems to stop pretty rapidly for whatever combination of reasons, but I've never tried to determine exactly how long. When I added a bunch of sand a while back, the pH dropped for a few hours, but with normal limewater additions over the next 24 h, the pH was back where it normally was.
Once the fouling has happened, you can add alkalinity as usual without any problems, and bicarbonate is a fine way.
<< Randy, Wouldn't that be a tempory effect with a longer term (hoursor/days)with a slight increase in alk? >>
The drop is, IMO, permanent until you add more alkalinity somehow. The ability of the sand to cause a drop is temporary. It lasts only a short time until enough magnesium/phosphate/organics get onto the surface and inhibit further precipitation of CaCO3.
bgdiving:
<< Thanks Randy, Would this be a one time event? or could it continue to cause alkalinity to drop untill biofouling accurred? I assume biofouling would start to show up in 3 to 4 days but could alkalinity continue to drop after that point until the sand particles are totally biocoated?>>
It seems to stop pretty rapidly for whatever combination of reasons, but I've never tried to determine exactly how long. When I added a bunch of sand a while back, the pH dropped for a few hours, but with normal limewater additions over the next 24 h, the pH was back where it normally was.
Once the fouling has happened, you can add alkalinity as usual without any problems, and bicarbonate is a fine way.
I take it that the sand would also be pulling Calicium as calicum carbonate but is it also pulling significant amounts magnesium and should that be replaced? I'm sure if its pulling phasphate no one is too concerned about loosing the phosphate from the water column but does it get locked up temporalily and later produce a problem when the water around the new sand becomes more acidic?
Ok, since I just got some sand from ESV via Bob Stark, I added (dumped) 3/4 of a bucket to a 30 gal tank. The dKH reading went from 12.8 to 19.8 using a salifert test. Usually I would clean the sand and add it a little bit at a time to the system, but I had to see what would happen. Sooooo I guess that the alkilinity increased.
Ill test again in a couple of hours.......
Ill test again in a couple of hours.......
One day later and my dKH for the entire system is at 14! The system includes the 30G,94G,90G 55G and a shared sump. I turned off the CO2 reactor before adding the sand. It would seem logical that adding the sand INCREASES alk especially since you are adding calcium carbonate sand. BTW, when I allowed the contents of the 30G to mix with the rest of the system, there were no PH changes, a reading I looked at 2 hours later on my 94G PH meter.
I set up a 20 gall tank with 4 inches of 90% new fine grain araganite sand and then added about a gallon of live sand from my 170 to serve as activator. when I replaced the sand in the 170 I used twice as much as I had removed.
When I tested the alk a wk later the new tank had an alk reading of less than 2 Meq which kind of surprised me, had used 10 gallons newly mixed instant ocean and 5 gallons of used old instant ocean. alos have been having difficulty maintaining my normal 3.5 to 4.0 Meq in the large tank and was wondering if adding new sand could be affecting the Alk. Sounds like it might be the cause.
When I tested the alk a wk later the new tank had an alk reading of less than 2 Meq which kind of surprised me, had used 10 gallons newly mixed instant ocean and 5 gallons of used old instant ocean. alos have been having difficulty maintaining my normal 3.5 to 4.0 Meq in the large tank and was wondering if adding new sand could be affecting the Alk. Sounds like it might be the cause.
randy holmes-farley
Advanced Reefer
- Location
- Arlington, MA
DK:
<< It would seem logical that adding the sand INCREASES alk especially since you are adding calcium carbonate sand. >>
Actually, that doesn't make sense to me at all. If it does to you, please explain it to me. The only explanation that I can believe is that the sand was contaminated with something besides calcium carbonate
Did you rinse it prior to use?
You don't report your calcium levels, but I expect that your tank, like everyone elses, is supersaturated with respect to calcium carbonate. That is, clacium carbonate does not dissolve in it, and will precipitate from solution if given the opportunity. This lowers alkalinity, not raises it.
This effect is well established in seawater: calcium carbonate does not dissolve.
<< It would seem logical that adding the sand INCREASES alk especially since you are adding calcium carbonate sand. >>
Actually, that doesn't make sense to me at all. If it does to you, please explain it to me. The only explanation that I can believe is that the sand was contaminated with something besides calcium carbonate
You don't report your calcium levels, but I expect that your tank, like everyone elses, is supersaturated with respect to calcium carbonate. That is, clacium carbonate does not dissolve in it, and will precipitate from solution if given the opportunity. This lowers alkalinity, not raises it.
This effect is well established in seawater: calcium carbonate does not dissolve.
randy holmes-farley
Advanced Reefer
- Location
- Arlington, MA
bgdiving:
<< I take it that the sand would also be pulling Calicium as calicum carbonate but is it also pulling significant amounts magnesium and should that be replaced? I'm sure if its pulling phasphate no one is too concerned about loosing the phosphate from the water column but does it get locked up temporalily and later produce a problem when the water around the new sand becomes more acidic? >>
pH will be a more sensitive indication of precipitation than will alkalinity, which will be more sensitive than calcium changes. So I expect calcium to drop, but maybe not by enough to notice in most cases.
Magnesium will drop very little. It will be absorbed, but is present in so much higher concentration in the water than is calcium (more than 5x on an ion basis), that I expect it to go undetected.
Phosphate is another story. It would be interesting to see what happens to orthophosphate when a bunch of new sand is added.
Yes, the phosphate could come back and bite you some day. Here's a thread where we discuss that situation:
http://www.reefcentral.net/vbulletin/showthread.php?s=6c4335ff300f2ce2a6bf727bb2a60d75&threadid=57169
<< I take it that the sand would also be pulling Calicium as calicum carbonate but is it also pulling significant amounts magnesium and should that be replaced? I'm sure if its pulling phasphate no one is too concerned about loosing the phosphate from the water column but does it get locked up temporalily and later produce a problem when the water around the new sand becomes more acidic? >>
pH will be a more sensitive indication of precipitation than will alkalinity, which will be more sensitive than calcium changes. So I expect calcium to drop, but maybe not by enough to notice in most cases.
Magnesium will drop very little. It will be absorbed, but is present in so much higher concentration in the water than is calcium (more than 5x on an ion basis), that I expect it to go undetected.
Phosphate is another story. It would be interesting to see what happens to orthophosphate when a bunch of new sand is added.
Yes, the phosphate could come back and bite you some day. Here's a thread where we discuss that situation:
http://www.reefcentral.net/vbulletin/showthread.php?s=6c4335ff300f2ce2a6bf727bb2a60d75&threadid=57169
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Randy Holmes-Farley:
<strong>DK:
<< It would seem logical that adding the sand INCREASES alk especially since you are adding calcium carbonate sand. >>
Actually, that doesn't make sense to me at all. If it does to you, please explain it to me.</strong><hr></blockquote>
<strong>DK:
<< It would seem logical that adding the sand INCREASES alk especially since you are adding calcium carbonate sand. >>
Actually, that doesn't make sense to me at all. If it does to you, please explain it to me.</strong><hr></blockquote>
Randy, I guess I need more work using the board.
My answer is that I understand that on a reef, the calcium levels are actually elevated where you would expect them to be depressed because of calcification "going on". Apparently, that is not the case, and a part of that result is due to mechanical breakdown by wave action and the various critters. I believe that the reason the alk went UP was because of the very very small particles in the sand that cause the white cloudiness. I did not "clean" the sand prior to adding it to the tank. Cleaning or rinsing actually removes those very small particles of calcium carbonate. I would also question what impurities that would possibly be in the sand that would raise the alk, either in the ESV oolitic sand product or for that matter, the southdown sand product.
My answer is that I understand that on a reef, the calcium levels are actually elevated where you would expect them to be depressed because of calcification "going on". Apparently, that is not the case, and a part of that result is due to mechanical breakdown by wave action and the various critters. I believe that the reason the alk went UP was because of the very very small particles in the sand that cause the white cloudiness. I did not "clean" the sand prior to adding it to the tank. Cleaning or rinsing actually removes those very small particles of calcium carbonate. I would also question what impurities that would possibly be in the sand that would raise the alk, either in the ESV oolitic sand product or for that matter, the southdown sand product.
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