Adding calcium chloride is the best way to raise it. This calculator shows how much, and the article guides you through the process:
Solving Calcium and Alkalinity Problems
http://www.advancedaquarist.com/issues/nov2002/chem.htm
Reef Chemicals Calculator
http://home.comcast.net/~jdieck1/chem_calc3.html
Here's the section from my upcoming article on the DIY recipe concerning substitutes and where to buy them:
Substitutes for Dowflake Calcium Chloride
If Dowflake calcium chloride or a repackaged version (such as All-Clear) cannot be located, Peladow or Dow Mini-Pellets, which are dehydrated versions of Dowflake (that is, they have less water in the crystals), can be substituted. In addition to the Peladow brand name, Peladow also is sold as Prestone Driveway Heat and possibly as some other common brands. Kent Turbo Calcium is also suitable and is an anhydrous calcium chloride. Any FCC (food), USP (pharmaceutical) or BP (pharmaceutical) grades of calcium chloride should be suitable.
Peladow, Dow mini-Pellets, Prestone Driveway Heat, Kent Turbo Calcium and other dehydrated calcium chloride products are more potent than Dowflake. The dehydration makes them both more potent by weight, and more dense, so they are much more potent by volume. The problem is that it is rarely clear how much moisture they contain. Peladow specifies 90% calcium chloride minimum, but it may be higher in some cases. Dow Mini-Pellets say 94% minimum, but actually have a lower bulk density than Peladow. The best guess for an amount to use is based on the hydration levels and bulk density provided by Dow for these products. Using these numbers, I suggest that aquarists use 20% less VOLUME of the dehydrated versions in the recipes than the Dowflake they call for. So a recipe calling for 5 cups of Dowflake would use 4 cups of Peladow, Prestone Driveway Heat, Kent Turbo Calcium, etc.
Choosing other unknown brands of any of the products may be fine, or not. Iââ"šÂ¬Ã¢"žÂ¢ve not tested them for purity.
Where to Buy the Materials
Baking soda (sodium bicarbonate) is best obtained from a grocery store to ensure that it is a food grade material. Arm & Hammer is a fine brand, as is a store brand. Be sure to NOT use baking powder. Baking powder is a different material that often has phosphate as a main ingredient.
Calcium chloride dihydrate (Dowflake) can often be obtained at stores such as Home Depot as a deicer. All-Clear calcium chloride for pools is repackaged Dowflake.
The following links lead to companies that are believed to supply Dowflake. Some will ship and some may be available only via local pickup:
http://www.buckeyefieldsupply.com/showproducts.asp?Sub=124&showspecials=124
http://www.flordrisupply.com/index2.html
http://www.mainstreetseedandsupply.com/saltproducts.htm
http://www.gemplers.com/a/shop/product.asp?T1=CACL2&src=21BR001
http://www.meltsnow.com/products-dry-calcium-chloride.htm
http://www.cal-chlor.com/products.htm
http://www.farrellequipment.com/catalog/ChemicalCementitious.pdf
Peladow is available from some of the suppliers above and is sold at many home products stores as Prestone Driveway Heat for deicing.
