Alkalinity / Sodium Carbonate Solidifying

I have used two part solution from Bulk Reef Supply in the past and have always been very happy with it.  Recently I am trying to raise my alkalinity with the sodium carbonate from around 2 meq/L to  3 meq/L with little success.  I had low Ca+ levels that have been correct with the help of Randy Holmes-Farley's great article on correcting alkalinity and calcium problems but have not been able to raise my alkalinity.  Our recent speaker suggested that alkalinity plays a large role in his success of reef tanks and growing SPS so I decided to focus a bit more on this aspect of my tank. 

I have noticed that when adding the sodium carbonate that it initially is cloudy as is expected but the milky cloud quickly solidifies into a solid. I can not seem to find any literature on this to see whether this is normal, I suspect that it is not normal as when chemicals solidify they tend to bind to something and become inactive which would be why I have been unable to raise the alkalinity in my tank.  I am hoping that someone can help me track down a solution to this problem.

I may resort to the manual addition of lime water but am hesitant because Randy strongly feels that this addition is not a correction for this type of alkalinity problem.  I added 100ml of sodium carbonate to my 30 gallon nano which is quite a bit and if I do not see a change in my testing tomorrow I think that I will have to conclude that something is wrong.   I have also discarded the batch of sodium carbonate mix and made a fresh one to see if some of my readings about temp. effects on sodium bicarbonate were the case, but no it is not.  Some suggested that cold will alter the effects but I store mine inside where temp. probably never get below 65 degrees.  Any suggestions would be appreciated.

 

I have also used the BRS 2 part solutions and I saw the same result unless I added the alkalinity part directly into a very strong water flow, like right in front of a pump outlet.  The strong water flow will allow it to blend in before it solidifies.

 

try 2 1/4 cups of baking soda baked in the over at 300 degrees for one hour mixed in RO water to make a gallon of solution.  Its cheap and easy and works just fine.  Never has caused an issue for me

 

Check your magnesium.  If you have low magnesium, you will have trouble raising your alk.

 

My Mg+ levels are at good levels. My question is not really about the raising of my alkalinity it is more about understanding why the carbonate is solidifying. I did large water changes todays as a part of my routine maintenance and ran across an old bottle of Purple Up which used Potash (K2O), Potassium Carbonate, as its alkalinity component.  I added several ml to the tank and it clouded up just as it should and did not solidify. I added about 5 ml of the potash to raise my alkalinity to near normal levels.  I will continue to do so to get to where I need. I plan on picking up some Arm & Hammer Super Washing Soda which is Sodium Carbonate with no surfactants or fragrances used by Randy Holmes Farley to test if a different source for the alkalinity resolves the problem.

As a side not Potassium Carbonate has a higher solubility than Sodium Carbonate with respect to temperature.  This may be a contributing factor the the reason for the solidification that I am seeing. 

Thanks for all the answers.

 

Call brandon at BRS and ask him...im curious to know and hes always been super helpful.

 

Then I'd try the baked baking soda as well.  What that process does is cook off the excess moisture.  

2 1/4 cups makes a gallon as said before.  I buy food grade baking soda at Sam's Club in a 5lb bag for $12.  This is what I've always used along with the BRS Calcium and Magnesium solutions.

 

i thought baking it changed it from sodium bicarb to sodium carb, which it turn increased potency...maybe i read that wrong...either way it works well!!

 

Baking off one of the carbonates keeps the pH from raising as much as you add it.  

Another question would be where are you adding the current solution?  Is it high or low flow?  

And another thought - have you tried another alkalinity test?  Yours may be off.

And what levels are your calcium and magnesium?

 

I use a nano 2 part for my tanks. if i dont wait long enough to put the part 2 in it will cloud and not disappear quickly like its supposed to.

 

If you will dilute the mixture down more it will not cloud and precipitate out like you are talking about.

I dose my Calcium and Alk components using a dosing pump. Instead of mixing the Sodium carbonate into only one gallon of water, I mix it with three gallons, so when my dosing pump goes to pumping it doesn't just create a big cloud that clumps and becomes useless.

 

Sam stopped by yesterday so that I could show someone else how my alkalinity was solidifying and just like when you take a care to the shop and the mechanic is waiting to hear that noise, it doesn't do it.  The alkalinity dispersed just as it is supposed to and with 50ml was able to raise my alkalinity to 8.0 dKH which it had not been at ever.  I am not developing a dosing statagy for the tank that may involve something like sdf_beanhead is talking about, it is just that I am so space limited in a nano.

 

Since we typically run our aquariums at a near saturated or even super saturated level of carbonate, it is not unusual for it to precipitate as you add it.  The problem is that when you dump it in, the local concentration, right there in the spot where it was dumped, goes sky high.  This leads to precipitation.  The problem is that once carbonate precipitates in your tank, it can't be redissolved, because it usually goes out as insoluble CaCO3.  The easiest remedy is to add your alk in a high flow area so that it gets dispersed before it precipitates.  The second key is to add slowly.  That's why a lot of people use dosing pumps.  If you just dump in 50ml of 2-part alk solution all at once, it is almost all going to precipitate.  Add it slowly a few ml at a time until it is in. 
Also worth noting is the local pH effect.  Right where you dump the alk in, the pH goes up or down depending on which recipe you use.  This can have a large affect on carbonate solubility right there in that local area.  The easy answer is to use a mixture of baking soda and baked baking soda to reach a buffer at your desired pH.  This requires some chemistry and some calculation though.  I think, but don't quote me on this, that if you use about 1 - 2% baked baking soda you come out around 8.3.  If anyone is interested, I can post the real calculation when I have a little free time.
 

 

Just on another note... I agree with the part of it needing to be added in a very high flow area.. I usually put mine into the overflow and let it be churned up and mixed in the sump and pumps. Also.. I have always tried to stick with the manufactures recomended doses but I have found that with ALk... It takes a LOT to just to get it to move a hair... I was doing it the regular way with no results for weeks before I just started dumping the stuff in .. it moved and nothing was hurt after that...

 

A note to clear up a little mis-information above.  Baking the baking soda removes water and carbon dioxide.  The reaction is  2 NaHCO3  ---->  Na2CO3  +  H2O  +  CO2.  It halves the amount of carbonate, but makes it a stronger base at the same time.  Check Farley for the exact amount that it changes the alkalinity raising ability.  It's not much.
As for pH, (referenced backwards above), baked baking soda will raise your pH as you add it.  Baking soda will lower pH as you add it.  This is a function of the pKa of carbonate.  pKa1 is around 6.5 and pKa2 is around 10 if I remember right.  So versus a pH of 8.3 in a reef tank, bicarbonate acts as an acid and carbonate as a base.  There are differences in solubility, but not huge. 
Another thing that will cause alkalinity not to take, (but will not cause the precipitation mentioned in the OP), is pH.  If the pH is too low, some of your alk will escape as CO2 if you only use carbonate/bicarbonate for alk.  For an extreme example, throw some vinegar on some baking soda and watch what happens.  It's not a fast process at pH > 7, but does occur as an equilibrium reaction (that is to say it goes both ways equally).  Since CO2 escapes to the atmosphere, the equilibrium gets shifted that direction and you lose even more. 
Na2CO3  <------>  NaHCO3  <------->  H2CO3 ------->  CO2 ^(escapes as a gas and can't go backwards)
Go look at some of the commercial additives out there for pH and alk.  Almost all include a source of hydroxide.  Usually a mix of NaOH and KOH.  This will raise the pH more than carbonate and the alk less than carbonate, and adds ZERO buffering capacity so most people don't see the reason for it.  But it is important because it shifts the equilibrium back towards carbonate, and at a pH>8.0 you don't have to shift it much to keep your alk in solution. 
I know I have stretched this topic a little, but I hope this helps some.