Hydrated Lime is Calcium Hydroxide. Also called Quick or Slaked Lime. Hy lime readily dissolves in water and is VERY caustic. It can raise your PH to over 12 in a matter of seconds. The chemical action is also very short lived and the PH will go back to "normal" after about a week or so.
Agricultural Lime is Calcium Magnesium Carbonate. Also called Dolomite, Dolomitic Limestone, and Road Rock, Ag Lime is FAR less caustic. Ag Lime dissolves VERY slowly by chemically reacting to neutrilize acids and is very slow to dissolve. Ag Lime is "Generally Considered Safe" for ponds as it can only raise the PH of water to a maximum of a very safe 8.2. Also Calcium and Magnesium are very beneficial to the growth of fish and these minerals "buffer" the daily changes in PH in a pond by neutrilizing mainly Carbonic Acid that is formed at night as plants respire. These two mineral salts directly affect and are measured as Alkalinity and Hardness.
EDIT: Hydrated Lime is only available as a very fime powder. Agricultural Lime is just crushed limestone and can come in many sizes or even in a "pelleted" form. Pelleted lime is often 50-60 times the price of crushed bulk lime.
Last edited by Rainman; 09/14/10 07:57 AM.
