Alk 2part not dissolving when dosed

[Flatlandreefer]

I am expierencing a minor issue/oddity when dosing two part. When I dose my alkalinity solution it creates flakes in the water instead of making a white cloud that quickly dissipates as it normally would.

I am using BRS two part and I have just started dosing as this is a newish tank that just started expierencing an alk drop.

The dosing is working and is bringing alkalinity levels up to where the the BRS calculator says they should elevate to but the flakes seem abnormal. I am dosing both parts at the same time but in separate areas of the sump, although I have dosed alk by itself with the same results.

Does anybody have a reason why the solution would flake like it does?

 

[Jrainey312]

Whats your magnesium level. Sounds like its precipitating out.

 

[Fumanchu]

Check calcium

 

[Justin Cook]

If they aren't in the alk solution but form when you add it to the tank, it does sound like it's precipitating out. However, it's not unusual for some flakes to be found in the alk solution itself. I think of them more as chunks but flakes work.

 

[Larry L]

I am dosing both parts at the same time but in separate areas of the sump, although I have dosed alk by itself with the same results.

Is there much flow near where you are dosing? It might help to try dosing into your tank near a powerhead, and dosing the two parts with more time between.

Whats your magnesium level. Sounds like its precipitating out.

Definitely worth bringing magnesium up first if it is low, it helps keep calcium and alkalinity from precipitating out of the water so that they stay available to your corals. BRS has a good video about it:

Magnesium: The magic that holds your reef tank together

 

[Flatlandreefer]

Whats your magnesium level. Sounds like its precipitating out.

Check calcium

If they aren't in the alk solution but form when you add it to the tank, it does sound like it's precipitating out. However, it's not unusual for some flakes to be found in the alk solution itself. I think of them more as chunks but flakes work.

I just checked all 3 major paramaters. My dosing pumps dosed the daily dose about an hour and a half ago so this is post dosing for the day.

DKH: 8.0 (where I want it and this has been stable since dosing)
Calcium: around 480 (salifert)
Magnesium: 1500+ (the test never changes colors when using the salifert test, above the testable range for salifert)

As for dosing in a high flow area, my calcium doses directly into a power head, and my alkalinity doses up stream from the return pump inlet so most gets sucked into the return. As I stated before my alkalinity creates these chunks/flakes regardless of whether it is dosed together or separate from calcium so that doesn't seem to be the issue, plus calcium is down stream from the alkalinity solution and the alkalinity portion has already turned into flakes before it gets to the calcium.

As for the solution in the dosing container, there are no flakes and everything is completely dissolved and clear, this only happens once it hits salt water.

 

[Larry L]

My dosing pumps dosed the daily dose about an hour and a half ago so this is post dosing for the day.

You might just be dosing too much too fast. Is it possible to split up your dosing over the course of the day into smaller amounts? I use an Apex to run my dosers so I dose a tiny amount every half hour, with the calcium and alk dosing offset by 15 minutes

 

[Flatlandreefer]

You might just be dosing too much too fast. Is it possible to split up your dosing over the course of the day into smaller amounts? I use an Apex to run my dosers so I dose a tiny amount every half hour, with the calcium and alk dosing offset by 15 minutes

I am only dosing roughly 10-12 ml total, 5 min using BRS dosing pumps which dose a little more than 2 ml/min

 

[Flatlandreefer]

I found this in an article by Randy Holmes-Farley on reefkeeping.com. If I understand this correctly, does this mean Magnesium could be precipitating out and later dissolving?


Precipitates When Carbonate Solutions are Added

Many aquarists are familiar with the cloudiness that forms when high pH two-part calcium and alkalinity additive systems are added to marine aquaria. Figure 3 shows the initial cloud that forms, for example, when the alkalinity part of B-ionic is added to a relatively low flow reef aquarium. The initial cloud sinks and spreads out, eventually dissolving. A similar phenomenon is not observed when adding calcium or magnesium salts, but is observed when adding sodium carbonate solutions.

This cloudiness is, at least in part, magnesium hydroxide and is formed when hydroxide ions are added and the local pH rises. Unlike the addition of limewater, which is unlikely to form magnesium carbonate, this may, although I think it unlikely. The reason it might form here is that the addition of the carbonate ions may push the magnesium carbonate solubility product above saturation. The precipitation of magnesium carbonate can be kinetically slow, just as the precipitation of calcium carbonate can be slow, and since this cloudiness forms instantly, magnesium hydroxide is a much more likely candidate. However, if the additive is not rapidly mixed in, or worse yet, if solid globs of the initial precipitate settle out and are very slow to dissolve, then conditions may be ripe for magnesium carbonate (and calcium carbonate) to form.

In any case, any magnesium carbonate that does form will probably dissolve later as the pH returns to normal reef aquarium levels, so whether the initial cloudiness contains any magnesium carbonate or not is not a critical issue. It does not contain calcium carbonate if mixed in reasonably quickly (a couple of minutes or less), as CaCO3 would not dissolve when mixed with seawater (and this material is observed to dissolve).

 

[Jordan pitts]

I have the same thing happening in my tanks as well and my parameters are
Alk:7
Calcium:480-500
Mag:1500+

 

[Ross Petersen]

Old thread here... ever find out what was causing the white small chunks of precipitate upon adding carbonate/alkalinity for dosing?!

I observed the same thing yesterday... high flow area, parameters in check, and lots of white little chunks dispersed throughout the tank...

 

[Dkeller_nc]

This is speculation, but perhaps provides some ideas for solving the issue.

The first thing I'd suggest doing is to filter your alkalinity solution through a coffee filter. If there are substantial amounts of dust or other debris in the alkalinity (solid) reagent, those can provide nucleation sites for precipitating noticeable amounts of magnesium carbonate, or even calcium carbonate from the tank water. It's probably a long shot, but it's easy to do, and eliminates one variable.

The OP noted that the calcium solution was dosed directly into a powerhead. Powerheads are substantially warmer than the tank itself because of the mechanical friction inherent in an operating powerhead. Precipitation of calcium carbonate is strongly dependent on temperature and the tank's levels of alkalinity and/or magnesium. At the very least, it's probably not good for the powerhead, as calcium carbonate is likely to precipitate on the moving parts of the PH.

Finally, it's probably worth capturing some of the flakes in a filter sock or fine-meshed net, and allowing them to stand in a clear glass of tank water (for easy observation). If they slowly dissolve, they may be magnesium carbonate that has precipitated out in larger particle sizes than normal, perhaps because of the high magnesium level. If they don't dissolve even after repeated stirring, they are probably calcium carbonate, which you could confirm by draining off most of the tank water and adding some vinegar or citric acid solution. If the flakes fizz strongly and dissolve, they are probably calcium carbonate.

 

[Ross Petersen]

This is speculation, but perhaps provides some ideas for solving the issue.

The first thing I'd suggest doing is to filter your alkalinity solution through a coffee filter. If there are substantial amounts of dust or other debris in the alkalinity (solid) reagent, those can provide nucleation sites for precipitating noticeable amounts of magnesium carbonate, or even calcium carbonate from the tank water. It's probably a long shot, but it's easy to do, and eliminates one variable.

The OP noted that the calcium solution was dosed directly into a powerhead. Powerheads are substantially warmer than the tank itself because of the mechanical friction inherent in an operating powerhead. Precipitation of calcium carbonate is strongly dependent on temperature and the tank's levels of alkalinity and/or magnesium. At the very least, it's probably not good for the powerhead, as calcium carbonate is likely to precipitate on the moving parts of the PH.

Finally, it's probably worth capturing some of the flakes in a filter sock or fine-meshed net, and allowing them to stand in a clear glass of tank water (for easy observation). If they slowly dissolve, they may be magnesium carbonate that has precipitated out in larger particle sizes than normal, perhaps because of the high magnesium level. If they don't dissolve even after repeated stirring, they are probably calcium carbonate, which you could confirm by draining off most of the tank water and adding some vinegar or citric acid solution. If the flakes fizz strongly and dissolve, they are probably calcium carbonate.

Hey - thanks for these insights. I'm going to experiment with a coffee filter (to explore the debris nucleation possibility). I'll also capture some precipitates to see if they dissolve.

I just read the precipitation article by @Randy Holmes-Farley (http://reefkeeping.com/issues/2005-07/rhf/index.php). Sounds like Mg(OH)2 precipitation is most likely. However, when I added the carbonate solution to my display tank 'snowflakes' of precipitate rather than a homogenous white solution was observed. The article suggests this may be a calcium and/or magnesium carbonate precipitate... if I interpreted reasonably.

Tank parameters: Magnesium 1550 (a bit high), alkalinity 7.5 dKH, temp 80F, calcium 430, etc.

I added the carbonate solution (mixed following BRS protocol) to a high flow MP40 area (away from the pump) so low flow and temperature are unlikely.

 

[Randy Holmes-Farley]

Old thread here... ever find out what was causing the white small chunks of precipitate upon adding carbonate/alkalinity for dosing?!

I observed the same thing yesterday... high flow area, parameters in check, and lots of white little chunks dispersed throughout the tank...

It is magnesium hydroxide. it happens with all high pH additives, until it is mixed in well and redissolves. It you allow it to settle out and sit for a while, you may also form some calcium carbonate locally, which will not redissolve.

:What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com
Figure 3. The transient cloud of magnesium hydroxide that forms when high pH additives are added. In this case, the alkalinity portion of B-ionic was added to a fairly still portion of one of my reef aquaria.

 

[Randy Holmes-Farley]

Hey - thanks for these insights. I'm going to experiment with a coffee filter (to explore the debris nucleation possibility). I'll also capture some precipitates to see if they dissolve.

I just read the precipitation article by @Randy Holmes-Farley (http://reefkeeping.com/issues/2005-07/rhf/index.php). Sounds like Mg(OH)2 precipitation is most likely. However, when I added the carbonate solution to my display tank 'snowflakes' of precipitate rather than a homogenous white solution was observed. The article suggests this may be a calcium and/or magnesium carbonate precipitate... if I interpreted reasonably.

Tank parameters: Magnesium 1550 (a bit high), alkalinity 7.5 dKH, temp 80F, calcium 430, etc.

I added the carbonate solution (mixed following BRS protocol) to a high flow MP40 area (away from the pump) so low flow and temperature are unlikely.

If you think it might be calcium carbonate, one way to tell is to add it to a large amount of seawater at normal pH and see if it dissolves. Calcium carbonate will not.

 

[Ross Petersen]

If you think it might be calcium carbonate, one way to tell is to add it to a large amount of seawater at normal pH and see if it dissolves. Calcium carbonate will not.

Thanks, going to give this a try - chemistry is compelling.