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How to Make 2-Part Dosing Solutions

If water changes aren’t keeping your calcium, alkalinity, and magnesium levels sufficiently high and stable, then it’s probably time you started dosing.  If you’re reading this without knowing your calcium, alkalinity, and magnesium levels, then stop.  Always test before you dose!  Dosing blindly can lead to coral browning, bleaching, or even death.

2-Part Dosing Chemicals

2-Part Dosing Chemicals

I take no credit for the chemistry behind these recipes.  Dr. Randy Holmes-Farley has several excellent articles on the subject, and I suggest you read them for additional information (article 1, article 2).  This article is just intended to guide you through the mixing.

2-Part Dosing Solutions

2-Part Dosing Solutions

[notice]Use caution throughout this project.  Although these chemicals are not overly dangerous, they are chemicals and can cause injury.  See links to Material Safety Data Sheets.[/notice]

Calcium (Randy’s Recipe):

I prefer to buy my calcium chloride in bulk from a known pure source.  Years ago many driveway deicing products were pure, but many toxic impurities have started showing up in some brands.  Although these impurities may be ok, there is no quality guarantee that the impurities won’t show up at very toxic levels some time in the future.  Some driveway deicing products are Prestone Driveway Heat, Dow Mini-Pellets, and Dowflake.  MSDS

Calcium Supplies

Calcium Supplies

  • 1 gallon RO/DI water
  • 2 ½ cups calcium chloride dihydrate OR about 2 cups anhydrous calcium chloride
  • Measuring cup
  • Clean food grade funnel
  • Plastic 1 gallon mixing jug (optional)
  • Plastic 1 gallon storage jug
  1. Add about half a gallon of RO/DI water to the mixing jug (or storage jug).
  2. Add the calcium chloride through the funnel.  [notice]Use caution here as the mixture can get quite hot.[/notice]

    Calcium Dihydrate on Left, Anhydrous on Right

    Calcium Dihydrate on Left, Anhydrous on Right

  3. Cap the jug and mix carefully.
  4. Add the remaining RO/DI water to the jug and mix again.

    Mixing Calcium

    Mixing Calcium

  5. Pour the solution into the storage jug if you wish.

    Calcium Storage Container

    Calcium Storage Container

  6. Use the handy reef calculator on the right side of the page to determine how much to dose based on your testing.

Alkalinity (Randy’s Recipe):

I prefer to use generic baking soda that I buy in bulk from the grocery store and bake it myself for Recipe 1; however, many aquarium stores sell it already baked.  Use caution as you pour the baking soda as it can be quite irritating to the nostrils.  MSDS

Alkalinity Supplies

Alkalinity Supplies

  • 1 gallon RO/DI water
  • 2 ¼ cups baked food grade baking soda (tanks w/ low pH) OR 1 1/8 cups baking soda (tanks w/ high pH)
  • Measuring cup
  • Clean food grade funnel
  • Plastic 1 gallon mixing jug (optional)
  • Plastic 1 gallon storage jug
  1. If your tank’s pH is less than 8.3, then bake 2¼ on a pan at 300°F for one hour.  Otherwise, you can use 1 1/8 cups unbaked baking soda.
  2. Add half a gallon of RO/DI to the mixing container (or storage container).
  3. Carefully add the baking soda through the funnel into the mixing jug (or storage container).
  4. Cap the jug, and shake gently until the solution is fully mixed.
  5. Add the remaining RO/DI water and mix thoroughly.
  6. Pour the solution into the storage jug if you wish.
  7. Use the handy reef calculator on the right side of the page to determine how much to dose based on your testing.  Choose “Recipe 1” if you used the baked baking soda.  Choose “Recipe 2” if you used unbaked baking soda.

Magnesium (Randy’s Recipe):

I prefer to use the magnesium chloride and magnesium sulfate recipe as the calcium impurities in the solution mix with the sulfates to precipate out.  Using magnesium sulfate alone can cause a buildup of sulfur in the aquarium.  I use Epsom salts that I purchase in bulk from a grocery store for magnesium sulfate.  I also choose to use magnesium chloride from a pure source.  There are magnesium chloride deicers, but again, the purity of many of these is unknown.  Use extreme caution if you use a source with unknown purity.  MSDS for magnesium chloride.  MSDS for magnesium sulfate.

Magnesium Supplies

Magnesium Supplies

  • 1 gallon RO/DI water
  • (5 cups Magnesium Chloride AND 3 cups Magnesium Sulfate) OR (8 cups Magnesium Sulfate)
  • Measuring cup
  • Clean food grade funnel
  • Plastic 1 gallon mixing jug (optional)
  • Plastic 1 gallon storage jug
  1. Add about half a gallon of RO/DI water to the mixing jug (or storage jug).
  2. Add the magnesium through the funnel.
  3. Cap the jug and mix carefully.
  4. Add the remaining RO/DI water to the jug and mix again.
  5. Pour the solution into the storage jug if you wish.
  6. Use the handy reef calculator on the right side of the page to determine how much to dose based on your testing.

1 comment

1 ping

  1. Pierre

    Nice, just what I was looking for, I also bought potassium carbonate for my alk mixture.

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