Fighting Algae with Borax

[waterbear]

To be effective it needs to be in the 30-50 ppm range. Adding borax for pH control generally will not get it into that range. You can probably purchase either the decahydrate or the pentahydrate form in bulk from a chemical supply. Here is a link for the decahydrate form (same as 20 mule team)
http://www.chemistrystore.com/borax.htm

Their prices are actually higher than the grocery store or walmart where you can buy a 4.75 lb box of 20 mule team borax for under $3!

Edit: To achieve 50 ppm borates in your 26k pool (assuming that no borates in the water) you would need 97.5 lbs (about 20.5 boxes of 20 mule team) and would need about 6 gallons of muriatic acid to bring the pH back in line and create the boric acid/borate buffer system in the water.