Using HCl to redissolve precipitated salt?

[Stelioshah]

I bought a new salt again that came to my door completely destroyed by moisture. I couldn't afford this for a second time so:

I mixed the salt in a bucket, collected all of the persipetaded solids using a canister filter, redissolved the solids in an HCl bath and then I neutralized the HCl, fixed the pH and the alkalinity, using NaHCO3 and Na2CO3 solutions.

After measuring Mg and Cal, both of their concentrations were a bit higher than usual, Mg was 1500ppm instead of the usual 1350ppm and Ca was 470ppm instead of the usual 450ppm (for the corresponding salt). (That probably is because a small amount of them always persipitates)

The HCl I used is sold as an HCl solution and nothing else. This procedure is much more efficient, way less expensive, way less time consuming and if it works way better than just fixing the Ca Mg and Alkalinity in a completely destroyed salt. Do you think it would be safe to use?

 

[Randy Holmes-Farley Verified Community Expert]

This seems like a big overkill procedure. If alk is low in a new salt mix, adding some alk is going to be easier.

What salt mix brand?

How low was alkalinity before you tried to redissolve solids?

FWIW, my normal IO salt mix always precipitated some solids, and I just ignored it since it had plenty of alk already and the effect on calcium is not that large.

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com

Figure 1. The residue on the bottom of the plastic trash can that I use to mix Instant Ocean. I rarely clean it out. The solid is most likely calcium carbonate.

 

[Stelioshah]

It is aquaforest reef salt. The thing is it is not just the Alk (which is at around 4-5dkH). The Ca is around 200ppm-250ppm and the Mg is around 700-800ppm without following the procedure. The salt is ruined completely. And the cost to fix Ca and Mg in such high depletion (repeated testing and dosing their respective salts) just make it not financially worth it. That's why I am following this procedure, otherwise it is financially better to just throw away the salt and buy a new bunch.

 

[Randy Holmes-Farley Verified Community Expert]

It is aquaforest reef salt. The thing is it is not just the Alk (which is at around 4-5dkH). The Ca is around 200ppm-250ppm and the Mg is around 700-800ppm without following the procedure. The salt is ruined completely. And the cost to fix Ca and Mg in such high depletion (repeated testing and dosing their respective salts) just make it not financially worth it. That's why I am following this procedure, otherwise it is financially better to just throw away the salt and buy a new bunch.

That is either a bad batch or test error. It cannot have come from precipitation. If the starting alk is 8 dKH, one cannot possibly precipitate more than 57 ppm of calcium becuase that would take the alk to zero, where no more precipitation of calcium carbonate is possible.

There is no scenario where magnesium can ever drop 600 ppm by precipitation or any other means.

 

[Randy Holmes-Farley Verified Community Expert]

Are you measuring salinity? Maybe you have only dissolved half the solids and you just need to stir longer.

 

[Stelioshah]

I just checked my numbers again because it was out of memory. I used to do weekly water changes, using said salt, by fixing both Ca and Mg. I used to dose 60-70 ppm of Ca in order to get it back to 430ppm and I used to dose 140-160ppm of Mg to get it back to 1300-1320ppm. I don't know what to tell you. I have wasted many different salifert test kits (different test kits for sure) during the procedure of dosing and testing in order to fix the salt and I always get similar results.

The last time I did a water change using said salt, the calcium was 350-360ppm, when on a fresh batch it is around 450ppm, and the magnesium was 1150ppm-1170ppm. My tests definitely show the aquaforest's expected numbers at 35ppt (using a good salt batch).

I dosed 6.2 grams of CaCl2*2H2O which raised my calcium by 60ppm (back to 420ppm) and I dosed 28.5g of MgCl2*6H2O which raised my Mg by 120ppm (back to 1290ppm). The total volume of water was 28.5 liters.

I don't know what to say. I have already wasted many hours dosing and fixing salt water again and again. I always get similar results with these salts. The previous numbers for the Mg might be excessive but I have definitely measured Calcium as low as 320-330ppm using salifert tests, based on some of my stored data.

The persipitated salt is not just a few flakes. It is a visible amount. I will weigh it next time I do a water change.

 

[Randy Holmes-Farley Verified Community Expert]

I don't know what to say either, but I am 100% certain that it is impossible to precipitate 200 ppm of calcium and 600 ppm of magnesium from new salt water, unless you added more than 150 dKH of alkalinity. There's just no source of carbonate to do anything close to that.

 

[Stelioshah]

So what do you think about the HCl solution? For me at least, is way less work. I am only afraid of the purity of the HCl, that's my only concern. The Cas number on the bottle shows HCl only thankfully.

 

[Randy Holmes-Farley Verified Community Expert]

So what do you think about the HCl solution? For me at least, is way less work. I am only afraid of the purity of the HCl, that's my only concern. The Cas number on the bottle shows HCl only thankfully.

I'm concerned about the whole scenario since I cannot see how it can happen, which makes me wonder about the underlying salt mix. There's a lot more to a mix than alk, calcium, and magnesium.

Did you track how much of how strong of an acid you added?

 

[BeanAnimal]

Curiously, why would it take so many test iterations to "get right"?

Wouldn't a single series of tests and calculated addition of major elements correct the numbers with possibly a single set of tests afterward for confirmation?

I purchase "solid" boxes of Instant Ocean at a huge discount from a local vendor because nobody else will buy them. I don't do regular water changes, so am not overly concerned about what does not dissolve. In the rare cases that I do a water change, I test and dose, just as I would with "new fully dissolved" salt anyway and that typically has HIGHER levels than what I run in my tank, so there is no "dosing".

Apologies if my comments sidetrack this conversation.

 

[Stelioshah]

Unfortunately not.. I tried this for the first time, just to see if I would encounter any problems so I added a random amount of 14-16% HCl. Then neutralized it by dosing NaHCO3 until bubble formation (CO2) stopped and the pH was around 7-8. In the final salt mix pH Mg and Ca were all in normal levels.

The reason I went with the procedure is because I already had a salt destroyed by moisture and bought a new one. The new salt arrived in the same situation which drove me mad. It used to take me 3-4 hours just to fix the levels of Ca Mg and Alk. And the tests are not cheap either. So I have 2 salts which have lost excessive amounts of these ions. I have had this only happen with aquaforest salts so I have no experience with the results in other salts.

The thing is that in the past, even after fixing the salt, my corals would still get mad when using it. I was wondering if something else persipitated as well which I didn't fix when dosing. But by using this procedure all of the solids are redissolved again, which means that I don't lose any ion.

Edit:
In the final salt mix the pH etc were all in normal levels after I fixed the Alk by dosing NaHCO3.

 

[BeanAnimal]

I will let you and Randy discuss the chemistry, it is beyond my pay grade. I will simply say that if it were me, I would just switch salt brands.

 

[Stelioshah]

Curiously, why would it take so many test iterations to "get right"?

Wouldn't a single series of tests and calculated addition of major elements correct the numbers with possibly a single set of tests afterward for confirmation?

I purchase "solid" boxes of Instant Ocean at a huge discount from a local vendor because nobody else will buy them. I don't do regular water changes, so am not overly concerned about what does not dissolve. In the rare cases that I do a water change, I test and dose, just as I would with "new fully dissolved" salt anyway and that typically has HIGHER levels than what I run in my tank, so there is no "dosing".

Apologies if my comments sidetrack this conversation.

The volume of the water that I make each time is not set, I would always make random volumes of salt water. In the end, I ended making an equation to make the calculations based in the height of the water and the total volume of the bucket. But even then, still, I would add the calculated solid slowly because it is better to underdose than overdose. You can't remove the excess amount but you can always add as much as you want. It would take even more time to make a new batch from scratch just the RODI needs 5-6 hours.

 

[Randy Holmes-Farley Verified Community Expert]

Unfortunately not.. I tried this for the first time, just to see if I would encounter any problems so I added a random amount of 14-16% HCl. Then neutralized it by dosing NaHCO3 until bubble formation (CO2) stopped and the pH was around 7-8. In the final salt mix pH Mg and Ca were all in normal levels.

The reason I went with the procedure is because I already had a salt destroyed by moisture and bought a new one. The new salt arrived in the same situation which drove me mad. It used to take me 3-4 hours just to fix the levels of Ca Mg and Alk. And the tests are not cheap either. So I have 2 salts which have lost excessive amounts of these ions. I have had this only happen with aquaforest salts so I have no experience with the results in other salts.

The thing is that in the past, even after fixing the salt, my corals would still get mad when using it. I was wondering if something else persipitated as well which I didn't fix when dosing. But by using this procedure all of the solids are redissolved again, which means that I don't lose any ion.

Edit:
In the final salt mix the pH etc were all in normal levels after I fixed the Alk by dosing NaHCO3.

Moisture cannot cause what you are seeing, unless you just did not wait long enough for the clumps to dissolve.

 

[Stelioshah]

Moisture cannot cause what you are seeing, unless you just did not wait long enough for the clumps to dissolve.

As I have said in an other post in the past, the aquaforest salt when getting wet, it turns from a white color to a light-bluish-green-white color. I have not the slightest idea what can cause this color (no copper leaks or anything, I am talking about a new batch). It could be that the crystals reflect light in such a way that it makes them look blue. I have no idea though.

The HCl batch was mixed for a day before adding the HCl and another day after adding.. I will use it.. Hope it works. Thanks for your help.

 

[Randy Holmes-Farley Verified Community Expert]

As I have said in an other post in the past, the aquaforest salt when getting wet, it turns from a white color to a light-bluish-green-white color. I have not the slightest idea what can cause this color (no copper leaks or anything, I am talking about a new batch). It could be that the crystals reflect light in such a way that it makes them look blue. I have no idea though.

The HCl batch was mixed for a day before adding the HCl and another day after adding.. I will use it.. Hope it works. Thanks for your help.

OK, let us know what you observe when using it.

 

[Stelioshah]

I would respond to this earlier, but I crashed my reef tank after dosing an alleged praziquantel solution, that ended up being non reef safe (because it contained other substances that were not mentioned on the package). In short, I killed all of my soft corals, but fortunately, I got rid of my aiptasia problem in the process aswell lol.

So, regarding this method. It is completely safe as I have observed. I have been using salt dissolved with HCl for months already. The HCl solution is 15% HCl and the brand is "AquaForte", the color of the solution is clear.

The steps of my method are:

First dissolve as much salt as its needed to reach your desired salinity (35ppt for me). Then use a CLEAN canister filter to collect the undissolved solids, I use an eheim biopower internal filter. If I have a large amount of water, I might need to empty the filter 2 or 3 times in seperate container. By "emptying" I mean removing the solids caught in the sponges by rubbing the sponges in a container (don't throw the solids away, these are what you need).

Note here: Regarding the aquaforest reef salt, for 450ppm Ca, just around 70-80% of the total undissolved solids are needed. If all of the solids are used, the water will reach Ca levels above 500ppm (and Mg above 1500ppm).

In the container with the solids, now add HCl until the solids are completely dissolved. The formed bubbles are just CO2.

After the solids are dissolved, neutralize the solution by adding baking soda (NaHCO3) or Na2CO3. In this step some percipitation (probably Fe(OH)3) occurs, giving the solution a brown-redish color and some more CO2 will be created. I measure the pH using a pH calculation paper.

After neutralizing, filter the solution through some cotton. The filtered solution should be clear. Add the liquid to your mixed saltwater in steps, measuring Ca and Mg between each step in order to reach the desired levels. In my case, If I dump the whole thing in the bucket, Ca and Mg levels fly off the chart.

Now, fix the alkalinity of your water. Given that your salt had percipitated, the alkalinity will be low.

Notes:

If your HCl solution is not CLEAR, DON'T use it.

If you neutralize AFTER filtering, it is likely that your solution won't be clear in the end.

After adding the dissolved solution, check the salinity of your water once again. The raise of salinity is negligible, but I still do test it with a refractometer.

For good measure I add a bag of carbon in the end, in order to adsorb any heavy metals that might have been introduced by the HCl solution. There are other better products for heavy metal adsorption in the market.

With this process, I don't notice any negative effects on my corals, fish or inverts. On the other hand, fixing manually the alkalinity, the calcium and the magnesium by dosing the elements on a persipitated salt, gave horrible results to me. My corals would die if I used said water repeatedly.

 

[Randy Holmes-Farley Verified Community Expert]

I’m not understanding why one would go to this effort.

 

[BeanAnimal]

I am honestly perplexed as well.

I would reiterate (if it were me) I would just switch salts.

 

[Stelioshah]

I just made a small amount of salt water just to provide the results. This saltwater has the exact same refractive index as a 35ppt high accuracy NaCl standard solution that I made, using high purity NaCl and the analytical equipement in the lab that I am a part of. The standard was made using the refractive index data at the Handbook Of Chemistry and Physics. To measure the refractive index, both solutions are at the exact same temperature. This proves that my test solution is actually 35ppt.

So the results once again. First of all, you can clrearly see in just 200mLs of water a significant amount of undissolved solids in the bottom. Calcium measures 370-375ppm instead of the usual ~450ppm of a good aquaforest reef salt batch in the same salt concentration.


Magnesium measures 1170ppm instead of the usual ~1380ppm in a good salt batch of the same salt.

The salt. The persipitated solids are obvious and considerable given the amount of salt needed to mix just 200mLs of salt:




The calcium. The first vial is the point where by salifert instructions 0.6mLs of the titration solution is added along with the solid powder. The second vial is the end point. The color is blue, the color of the photo is not that accurate. The measurement is 0.26-0.25 remaining mLs, so 370-375ppm Ca:




The magnesium. The measurement is 0.22mLs so 1170ppm:


You can clearly see the huge amount of undissolved solids in just 200mLs of water. As I have already mentioned, I used to fix Ca, Mg and Alk manually for months, using the conventional methods, by dosing CaCl2, MgCl2 and NaHCO3. In the end, although the Ca, Mg and Alk measurements were always corrected before using the water, (I never got an ICP test), my corals would still recede after a few weeks of repeated use of said water.

This result screams to me that some other element(s), that I am neither measuring nor dosing has/have persipitated as well. By using this method I ensure that I get ALL of the elements back into my water.

The method is WAY less work that manually fixing Ca and Mg. Everything is done with ease. If I were to fix the water by dosing, I would have to dose some Ca, wait for it to get mixed well and test the water. Oh the concentration is not there yet. I would need to redose, and remeasure again, and so on. Then I would have to do the same for Mg and Alk. And NO you cannot accurately measure the necessary amount of CaCl2 or MgCl2 needed, in order to fix the water beforehand. That is because you can never know the accurate molecular weight. What CaCl2 do I have? CaCl2? CaCl2*H2O? CaCl2*2H2O? and so on... How much moisture does my solid have? My MgCl2 trapped so much moisture recently, that there is literal liquid water in the bag.

This method takes more time, BUT, is WAY LESS work. The only thing you need to do is collect the solid (which is done automatically by a canister filter), dissolve the solid, neutralize it, filter it and fix the Alk, this is it. It is CHEAPER, way more accurate and in the meantime you ensure that whatever has persipitated, is what is added back into the water. Salifert tests are EXPENSIVE, CaCl2 and MgCl2 are not that cheap either, while HCl is basically free.

These results are reproducible between 2 seperate persipitated salifert batches and between multiple salifert test kits, that I wasted while using the conventional methods. I have been successfully using a salt batch that I had packed in order to throw it away, after fixing it with this method.

This post is made for people who experience the same issues with me. When aquaforest salts are sold in a box instead of a bucket, they arrive in this situation, because moisture gets trapped in, even before they are opened. I cannot speak of other salt brands as the only experience I have is with aquaforest reef salt (regarding this situation).