Aquarium Chemistry Question? Ask the Doctor!

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by revhtree, Mar 22, 2016.

  1. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    You're welcome.

    Happy Reefing. :)
     
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  2. Gareth elliott

    Gareth elliott Well-Known Member NJRC Member

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    What are your thoughts on the safety of using of glutaraldehyde for algae treatment in a reef system? Or if is even useful at the ph of a reef tank as opposed to the ph of most planted aquariums?
     
  3. Scott.h

    Scott.h Valuable Member Build Thread Contributor

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    Randy, I'm putting two heaping tablespoons of kalk in about a quart and a half of vinegar. I believe this should be fully saturated, as there is a slight slurry residue at the bottom. What would you consider the ph of this solution to be?

    I've been seeing dips in my ph below 7.70 dosing 40 ml a day of this solution in 100 gallons of water.. skimmer line ran outside, fuge, window cracked etc etc. My probe may need recalibrated as well. I've backed off from 55 ml to 40 ml with no difference.

    If you think this sounds like a realistic problem/possible scenario, my question then becomes which situation is the lesser of the two evils? Nitrates at 80 with a ph of always over 7.8, or nitrates at 30 with a ph dipping below 7.7 and regularly under 7.8? I have calibration packets coming.
    Thanks in advance
     
  4. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    What are you trying to accomplish, Scott?

    Saturating vinegar is a good way to add organic carbon, but not a good way to boost pH.
     
  5. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Gluteraldehyde as a source of organic carbon, or as a reactive molecule to kill something? I know freshwater folks talk about it, but I'm not sure they understand the effects it has.
     
  6. Gareth elliott

    Gareth elliott Well-Known Member NJRC Member

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    In freshwater in addition to organic carbon, we also commonly use to treat certain forms of algae, specifically green hair algae. Perhaps through enzyme immobilization or some other process?

    https://www.biotechniques.com/multimedia/archive/00037/BTN_A_04375RV01_O_37190a.pdf a
     
  7. Scott.h

    Scott.h Valuable Member Build Thread Contributor

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    My only goal with adding kalk was to help offset the ph drop using vinegar alone causes. I thought since kalk has such a high ph it would accomplish more of a neutral ph of the vinegar. Is this not the case?
     
  8. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    OK, for that purpose, it's a good way to go. I did it,a nd its a good way to go when manual dosing once or twice a day. But I think you may need more calcium hydroxide. To saturate a liter of vinegar takes about 63 grams of calcium hydroxide. Adding twice that is also fine, then just reuse the solids. But don't assume it is saturated just because there is sold material solid present. It might just be calcium carbonate or magnesium hydroxide, both of which are typically present in calcium hydroxide.
     
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  9. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    I've never really been a fan of these sort of nonspecific treatments (e.g., hydrogen peroxide, etc.) unless one is fairly desperate (like a bad dino problem) since these processes impact the exposed tissues of every organism in the tank. :)
     
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  10. Gareth elliott

    Gareth elliott Well-Known Member NJRC Member

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    Thanks randy,
    My co2 solenoid broke and while waiting for the new one was using in my planted, Poor substitute lol.
    Made me wonder why i have never seen its use stated on a marine tank.
    Figured i would ask.
     
  11. Scott.h

    Scott.h Valuable Member Build Thread Contributor

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    I didn't realize a liter could absorb 63 grams. That's the missing link to my issue. Thank you for that.
     
  12. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    It only does in vinegar (or other acids), not in pure water.

    The solubility limit is hit when the multiplication product of the hydroxide concentration times the hydroxide concentration again times the calcium concentration hits a critical value.

    Ksp = [OH-] x [OH-] x [Ca++]


    When there is acid present, as from the vinegar, the H+ from the acid immediately reacts with OH- to produce water, depleting the hydroxide:

    H+ + OH- --> H2O

    So you have to keep adding calcium hydroxide until all the acid from the vinegar is used up, before you can attain saturation.
     
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  13. ericbost23

    ericbost23 Active Member Build Thread Contributor

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    So I have an issue in figuring out how much soda ash to raise the ph. The calculator ask for the current alkalinity in dkh. My test kit uses ph is there a difference
     
  14. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    You should not dose it in amounts to raise pH. Alkalinity is the driving concern,a nd it is an alkalinity supplement. Use it to boost alkalinity when needed, and you get whatever pH boost is there. But you should not ever determine the amount to use to figure a pH boost.

    That said, for each 1.4 dKH of alkalinity added, it will immediately, and perhaps temporarily, boost pH by about 0.35 pH units.

    These discussions explain what these parameters represent:

    https://www.reef2reef.com/threads/o...-reef-aquarium-by-randy-holmes-farley.173563/

    Alkalinity

    Like calcium, many corals also use "alkalinity" to form their skeletons, which are composed primarily of calcium carbonate. It is generally believed that corals take up bicarbonate, convert it into carbonate, and then use that carbonate to form calcium carbonate skeletons. That conversion process is shown as:

    HCO3- → CO3-- + H+

    Bicarbonate → Carbonate + proton (which is released from the coral)

    To ensure that corals have an adequate supply of bicarbonate for calcification, aquarists could just measure bicarbonate directly. Designing a test kit for bicarbonate, however, is somewhat more complicated than for alkalinity. Consequently, the use of alkalinity as a surrogate measure for bicarbonate is deeply entrenched in the reef aquarium hobby.

    So, what is alkalinity? Alkalinity in a marine aquarium is simply a measure of the amount of acid (H+) required to reduce the pH to about 4.5, where all bicarbonate is converted into carbonic acid as follows:

    HCO3- + H+ → H2CO3

    The amount of acid needed is equal to the amount of bicarbonate present, so when performing an alkalinity titration with a test kit, you are “counting†the number of bicarbonate ions present. It is not, however, quite that simple since some other ions also take up acid during the titration. Both borate and carbonate also contribute to the measurement of alkalinity, but the bicarbonate dominates these other ions since they are generally lower in concentration than bicarbonate. So knowing the total alkalinity is akin to, but not exactly the same as, knowing how much bicarbonate is available to corals. In any case, total alkalinity is the standard that aquarists use for this purpose.

    Unlike the calcium concentration, it is widely believed that certain organisms calcify more quickly at alkalinity levels higher than those in normal seawater. This result has also been demonstrated in the scientific literature, which has shown that adding bicarbonate to seawater increases the rate of calcification in some corals. Uptake of bicarbonate can consequently become rate limiting in many corals. This may be partly due to the fact that the external bicarbonate concentration is not large to begin with (relative to, for example, the calcium concentration, which is effectively about 5 times higher).

    For these reasons, alkalinity maintenance is a critical aspect of coral reef aquarium husbandry. In the absence of supplementation, alkalinity will rapidly drop as corals use up much of what is present in seawater. Water changes are not usually sufficient to maintain alkalinity unless there is very little calcification taking place. Most reef aquarists try to maintain alkalinity at levels at or slightly above those of normal seawater, although exactly what levels different aquarists target depends a bit on the goals of their aquaria.

    Interestingly, because some corals may calcify faster at higher alkalinity levels, and because the abiotic (nonbiological) precipitation of calcium carbonate on heaters and pumps also rises as alkalinity rises, the demand for alkalinity (and calcium) rises as the alkalinity rises. So an aquarist generally must dose more calcium and alkalinity EVERY DAY to maintain a higher alkalinity (say, 11 dKH) than to maintain 7 dKH. It is not just a one-time boost that is needed to make up that difference. In fact, calcification gets so slow as the alkalinity drops below 6 dKH that reef aquaria rarely get much below that point, even with no dosing: natural calcification has nearly stopped at that level.

    In general, I suggest that aquarists maintain alkalinity between about 7-11 dKH (2.5 and 4 meq/L; 125-200 ppm CaCO3 equivalents). Many aquarists growing SPS corals and using Ultra Low Nutrient Systems (ULNS) have found that the corals suffer from “burnt tips†if the alkalinity is too high or changes too much. It is not at all clear why this is the case, but such aquaria are better served by alkalinity in the 7-8 dKH range.
    As mentioned above, alkalinity levels above those in natural seawater increase the abiotic precipitation of calcium carbonate on warm objects such as heaters and pump impellers, or sometimes even in sand beds. This precipitation not only wastes calcium and alkalinity that aquarists are carefully adding, but it also increases equipment maintenance requirements and can “damage†a sand bed, hardening it into a chunk of limestone. When elevated alkalinity is driving this precipitation, it can also depress the calcium level. An excessively high alkalinity level can therefore create undesirable consequences.

    I suggest that aquarists use a balanced calcium and alkalinity additive system of some sort for routine maintenance. The most popular of these balanced methods include limewater (kalkwasser), calcium carbonate/carbon dioxide reactors, and the two-part/three part additive systems.

    For rapid alkalinity corrections, aquarists can simply use baking soda (sodium bicarbonate) or washing soda (sodium carbonate; baked baking soda) to good effect. The latter raises pH as well as alkalinity while the former has a very small pH lowering effect. Mixtures can also be used, and are what many hobby chemical supply companies sell as “buffersâ€. Most often, sodium carbonate is preferred, however, since most tanks can be helped by a pH boost.

    pH

    pH is a measure of the concentration of protons (H+ ions) and hydroxide (OH-) ions in the water. Aquarists spend a considerable amount of time and effort worrying about, and attempting to solve, apparent problems with the pH of their aquaria. Some of this effort is justified, as true pH problems can lead to poor animal health. In many cases, however, the only problem is with the pH measurement or its interpretation. Moreover, the maintenance of appropriate alkalinity in seawater goes a long way to ensuring that the pH is acceptable, with just a couple of exceptions that will be discussed below.

    Several factors make monitoring a marine aquarium's pH level useful. One is that aquatic organisms thrive only in a particular pH range, which varies from organism to organism. It is therefore difficult to justify a claim that a particular pH range is "optimal" in an aquarium housing many species. Even natural seawater's pH (8.0 to 8.3) may be suboptimal for some of its creatures, but it was recognized more than eighty years ago that pH levels different from natural seawater (down to 7.3, for example) are stressful to fish. Additional information now exists about optimal pH ranges for many organisms, but the data are inadequate to allow aquarists to optimize pH for most organisms which interest them.

    Additionally, pH's effect on organisms can be direct, or indirect. The toxicity of metals such as copper and nickel to some aquarium organisms, such as mysids and amphipods, is known to vary with pH. Consequently the acceptable pH range of one aquarium may differ from another aquarium, even if they contain the same organisms, but have different concentrations of metals.

    Changes in pH nevertheless do substantially impact some fundamental processes taking place in many marine organisms. One of these fundamental processes is calcification, or deposition of calcium carbonate skeletons, which is known to depend on pH, usually dropping as pH falls. At a low enough pH (somewhere below pH 7.7) coral skeletons can begin to slowly dissolve. Using this type of information, along with the integrated experience of many hobbyists, we can develop some guidelines about what is an acceptable pH range for reef aquaria, and what values push the limits.

    The acceptable pH range for reef aquaria is an opinion rather than a clear fact, and will certainly vary with the opinion's provider. This range may also be quite different from the "optimal" range. Justifying what is optimal, however, is much more problematic than is justifying that which is simply acceptable, so we will focus on the latter. As a goal, I'd suggest that the pH of natural seawater, about 8.2, is appropriate, but coral reef aquaria can clearly succeed in a wider range of pH values. In my opinion, the pH range from 7.8 to 8.5 is an acceptable range for reef aquaria.

    In truth, many aquarists never measure pH, and many that do so do not do anything with the results they obtain. This lack of action is usually okay, as most aquaria do not naturally fall outside of the acceptable ranges. Times when it is most important to at least check pH once in a while are:

    1. When using very high pH additives, such as limewater (kalkwasser). In this case, one should ensure that the pH does not get above about 8.55. At higher values, the precipitation of calcium carbonate on pumps and such can become excessive. Every 0.3 pH unit rise in pH is equivalent to about a doubling of the calcium or alkalinity value in terms of the likelihood of precipitation of calcium carbonate (because bicarbonate turns into carbonate as the pH rises, driving precipitation). Aquaria may often get to a pH that is high enough to double the precipitation rate due to elevated pH, but one does not often see aquaria with calcium or alkalinity that is double the normal value, making high pH a big driver of precipitation.

    2. When the air around the aquarium has elevated carbon dioxide levels, such as in a newer, tighter home. Low pH due to elevated carbon dioxide in the air is VERY common. While it may be useful to ensure the pH stays above 8.0, there are many fine aquaria with the bottom end of the pH range at pH 7.8. Below that value, I'd want to take more aggressive action, such as more fresh air in the home, top off with limewater (kalkwasser), a fresh air line from outside to a skimmer inlet, or a CO2 scrubber on a skimmer inlet.
     
  15. BigJohnny

    BigJohnny Valuable Member

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    Randy, can I prepare a stock solution of Potassium (Potassium Chloride Anhydrous and Potassium Sulfate Anhydrous), Strontium (Strontium Chloride Anhydrous), and Triton Base Iodine (I can't figure out what form/forms are in it)? I currently maintain all 3 separately but it would be nice to combine them into one solution, assuming it would be a homogeneous mixture and I would be able to predict how much I was dosing of each per mL. I also don't want any chemical reactions/precipitation occurring, obviously.

    Thanks!
     
  16. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Yes, those should mix fine.

    The one issue with dilution an iodine supplement is that it may make it more prone to air oxidation, so I- may become iodate over time.
     
  17. BigJohnny

    BigJohnny Valuable Member

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    OK thanks.
     
  18. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    You're welcome.

    Happy Reefing. :)
     
  19. BigJohnny

    BigJohnny Valuable Member

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    Quick follow up actually, can iodate be used the same way as iodine (I assume no) and would it show up on icp as iodine anyway?

    I realized I would not be able to track how much was iodate (if it matters) vs iodine (not that I really can now anyway but at least I know it's starting as iodine when I dose it). I am just trying to maintain nsw levels and my tank has consistently shown a reduction in iodine over time. I have a salifert test but rely on triton icp instead because I think I read that the hobby grade is basically useless for some reason.

    OR is it not even really a concern because the % of iodine that would oxidize over time would be so minimal? Is there anyway to estimate this based on the strength of triton iodine and the dilution % I utilize? Assuming stored in glass water bottle for example?

    Thanks!
     
  20. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Article Contributor Expert Contributor

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    Iodate (IO3-) and iodide (I-) are the predominant forms in seawater, with a slight excess of iodate. It is generally believed that iodate is less bioavailable.

    The reactions with air can first form I2 from iodide and this material can react in other ways, depending on what is int he solution. if you keep the solution closed and int eh dark, it will likely be OK. :)
     
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