Help reducing alkalinity

Discussion in 'Reef Chemistry by Randy Holmes-Farley' started by saltwaterer, Aug 15, 2017.

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  1. saltwaterer

    saltwaterer New Member

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    Hi, I'm just cycling my tank and when I measured the alkalinity two times at a week's gap it came to somewhere around 5.5 meQ/L, pH is a stable 8.2, Salinity is 34ppt. I use Continuum Halcyon Marine Reef Salt. I intend to use it as FOWLR for the time being. Could someone please help in the following:

    1. I know alkalinity is high but what range do you suggest for a FOWLR. Does it change with corals?

    2. How to lower it safely for the fishes? I've heard about Muriatic acid, Sodium bisulphate, vinegar. Do these products not affect fishes at all? Or is it like anything acidic be used?

    3. Will Sodium bisulphate add sulphur that is harmul to fishes? I'd prefer it due to being safe to use for myself, no fumes, burn risk etc. and possibly easier to obtain. I also read somewhere that it reduces pH only and alkalinity is mostly left untouched unlike muriatic acid, which reduces both. Is it possible?

    4. If the pH is lowered by any of these will it return back to 8.2 later, while the alkalinity is reduced to within the range. How much time will it take to rebound to normal and will I have to intervene in the process?

    5. How much to add and in what manner?

    6. Will adding any of these interfere with the cycle, ammonia, nitrites, nitrates or any other parameter that I'll have to take care of? Will the good bacteria survive?

    7. How to raise alkalinity in case of an acid overdose? Baking soda?

    8. Anything else important I'm missing.

    Thanks.
     
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  2. Randy Holmes-Farley

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

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    Some of the chemicals you mentioned (e.g., vinegar) won't work, so be careful where you get chemical advice.

    Have you measured the alk in your salt mix? The tank likely matches it (unless you are adding buffers) and letting the alk drop on its own and/or switching to a different mix is a reasonable plan.
     
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  3. Randy Holmes-Farley

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

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    Sodium bisulfate is a fine product to use with no side effects (aside from temporary low pH), assuming it is adequately pure.
     
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  4. saltwaterer

    saltwaterer New Member

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    Well I'm new to saltwater, all the info I got is by reading here and there, some of it is even contradictory. I've been following R2R for some time and trust your opinion the most on such issues. :) No buffers added. In future I may switch to a different mix but currently I have my tank full and cycling, so probably my only option is to add something. Automatic drop is something I've not heard about. Can you elaborate please.

    Could you let me know how much Sodium bisulphate to use and in what manner? Also will it be okay with the BB and the cycling?

    Last one, just out of curiosity, will it not introduce sulphur?

    Thanks a lot Randy.
     
  5. Randy Holmes-Farley

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

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    The contradictory information on things that are clearly cut and dried is why I started the various Reef Chemistry forums. The amount of incorrect info is a lot less today than 10-20 years ago, but it is still around. Even some big names have expounded on clearly incorrect things. One of these was the recommendation to lower alkalinity by adding CO2 via seltzer water. It cannot work, yet was touted by one of the leading "experts" for many years.

    Sodium bisulfate is NaHSO4. After depleting alkalinity, it will leave sodium and sulfate in the seawater. Since these are already the second and third most abundant ions in seawater (by weight), you will not noticeably impact them even if you deplete all the alkalinity this way.

    The molecular weight of anhydrous NaHSO4 is 120 grams/mole.

    So 1 gram will provide 1/120 moles of acidity, or 0.0083 equivalents or 8.3 milliequivalents.

    Adding 1 gram to 100 liters of aquarium water will drop alkalinity by 8.3 meq/100 L = 0.083 meq/L = 0.23 dKH.

    It will cause a pH drop so spread it out.
     
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  6. saltwaterer

    saltwaterer New Member

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    Okay there is a minor(probably) issue, instead of anhydrous, only monohydrate sodium bisulfate is available at my end. I guess that will do without issues. Adding 1 gram to 100 liters of aquarium water will drop alkalinity by 0.072 meq/L. Please let me know if I'm not cent percent correct. Thanks.
     
  7. Randy Holmes-Farley

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

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    Use 15% more of the hydrate to achieve the same results (multiply by 1.15). :)
     
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  8. saltwaterer

    saltwaterer New Member

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    Ok Thanks. :cool: Sounds good.
     
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