Calcium Drop Out

[Gazbo72]

I,ve dropped a bit of a booboo

When doing my regular water change I was making my water/salt mix up and I usually put two 5ml spoons of kent buffer in with the Tropic Marin Reef salt that I usually use. This time though I have used Red Sea Reef Pro as the LFS didn,t have my normal salt, I have done the same with this salt and when I got up this morning and looked in my mixing tub to see the sides, bottom, heater and power head all have gone white

Now the questions is the mix knackered or could I double the amount of water being used to bring it back and will the calcium percipitate back into the water or will I have to put dose the calcium bak up to normal levels

Advice will be much appreciated Gaz.

 

[SkiFletch]

Ah, to those whom have learned about preceipitation.

Lets see if I can explain this in a manner that makes sense... First off, a basic chemistry lesson. There are 5/6 major ionic components in the salt mixes we use (in order of concentration): Chloride, Sodium, Magnesium, Carbonate/Bicarbonate (aka alkalinity, aka buffer), and Calcium. Our salt mixes are designed so that when the mix is added, all those ions dissolve into solution. No salt mix is perfect, and some of them have certain ions in higher concentration than natural sea water (NSW) while others are lower than normal. Still with me? good

The significant relationship you have discovered here is that of saturation, supersaturation, solubility, and reactive potential. Water can only hold so many ions (or solids) dissolved into solution before it can't dissolve any more. For example, if you take a cup of water and start adding in teaspoons of sugar or salt, eventually the sugar and salt will no longer dissolve into the water, no matter how much you stir it. That point just before you can no-longer dissolve the solid is called saturation. The more kinds and types of solids/salts you dissolve, the saturation point of the individual solids becomes lower. It's like trying to stuff full a pantry with food. You can fill the whole thing with a LOT of flour, but what if you want cookies? Gotta take out some flower to make room in there...

So, because NSW has so many ions, it tends to be very close to the saturation point of every ion in solution. Additives however are typically a mixture of one salt/ion and water (a pantry full of buffer for example). So much so that additives can be concentrated tens of thousands of times more of their specific ion then you will find in NSW. So when you add that liquid additive into your freshly mixed water, you CAN get to a point of supersaturation (an overflowing pantry). When supersaturation occurs, one, some, or all of the ions in the mixture must somehow come out of solution and re-form as solid salts.

So in your example, you had a different salt variety that was probably close to NSW or perhaps even a little higher as far as buffer concentration goes. When you then added buffer, you supersaturated it in solution (put too much in), and it went through a favorable chemical reaction to make a salt. Specifically, when supersaturation of buffer (carbonate/bicarbonate/alkalinity) OR, Calcium occurs in a seawater solution, the dissolved Calcium and Bicarbonate ions will form solid Calcium Carbonate Salt (Ca2+ + 2CO3 --> Ca2CO3). Once started the reaction is rapid and can "crash" the dissolved values of each component. That white stuff you see on all your surfaces is Calcium Carbonate Salt. Problem is, Calcium Carbonate is very in-soluble in seawater, meaning it will not go back into solution at the pH of seawater. If you make it acidic, it will re-dissolve back into solution (this is essentially how calcium reactors run).

So, in your situation, my guess is that the Red Sea Reef Pro has more than enough carbonate allready in its mix, and there's no need to add extra kent buffer to it.

Hope that made sense.

 

[Musho3210]

It would have been simpler for me if you just said "There was probably too much buffer in the water and it precipitated into buffer snow"

 

[SkiFletch]

yeah but then he wouldn't know why and he'd keep asking the question every time he tried a new salt and got the same result

 

[Gazbo72]

Great reply Ski

I have tested the water and the only thing that was a bit low was the calcium, So I have decanted the water into another tub leaving the undisolved Calcium Carbonate was in the old tub then cleaned the tub of the residue put the water back in and got the calcium back up to 420ppm. I,m going to leave it mixing for another 24 hours and retest it before doing a water change.

 

[sophos9]

Might be a stupid question but did you add the water first, then the salt?

 

[Gazbo72]

Might be a stupid question but did you add the water first, then the salt?

I put the water in the mixing tub then put the salt in slowly over the power head (Koralia2) to mix it once the water is up to temp.

 

[SkiFletch]

Sounds good Gaz. Btw, in the future if ever dealing with calcium carbonate deposits that are stubborn, go ahead and use vinegar or for really stubborn deposits, you can use some acid (sulfuric is commonly purchased as a plumbing cleaner, although exceptionally strong). Obviously you should never use acids, especially strong ones, on any water or equipment that ends up in your tank (equipment can be acidwashed, just make sure you rinse it thoroughly in tap then RO )

 

[Musho3210]

muratic (spelling) is also commonly used if vinigar isnt strong enough.

 

[SkiFletch]

MurIatic (HCl marketed to gunnite pool users )

 

[Musho3210]

dang, i got manipulated by monopolizing corporations....

 

[SkiFletch]

Heh, nah that's just marketing

 

[jeasko]

Ski
correct me here on my thinking (taking scuba practices into fish keeping!) but couldnt you avoid supersaturation by pressuring the water which would then raise partial pressures of different eliments within the water then gradually bring it back to one ata (atmospheric pressure) which would then allow all elements to be dissolved providing this is done at the correct rate (im not even going to go into working that one out!)

And before anyone says anything I know there is one major floor (and probably a few more and besides why would you bother!) with this as its asking alot to pressurize anything to the extent required, all im trying to do is see if i understand the principles surrounding supersaturation and seeing if the principles cross boundaries into the fish keeping world

 

[SkiFletch]

Great in theory jeasko, but there's two flaws in that logic. First, saturation and supersaturation apply to solids dissolved in liquid solution, partial pressures are only to gasses mixed in each other or in solution. Because calcium, carbonate, magnesium, etc are solids before being dissolved, they cannot have a partial pressure. The other flaw in the logic is that you can't pressurize water . Water is an icompressible liquid, thus the solids dissolved in it cannot be exposed to pressure