Algae – Microscopic plant-like organisms that contain chlorophyll. Algae are nourished by carbon dioxide (CO2) and use sunlight to carry out photosynthesis. It is introduced by rain or wind and grows in colonies producing nuisance masses. Algae are not disease-causing, but can harbor bacteria, and it is slippery. There are 21,000 known species of algae. The most common pool types and black, blue-green, green and mustard (yellow or drawn). Pink or red-colored algae-like organisms exist but are bacteria and not algae. Maintaining proper sanitizer levels, shocking and super chlorination will help prevent its occurrence.
Algaecide – Also called algicide – A natural or synthetic chemical designed to kill, destroy or control algae.
Alkali – Also called base – A Class of compounds which will react with an acid to give a salt. Alkali is the opposite of acid.
Alkalinity – Also more commonly called total alkalinity. A measure of the pH-buffering capacity of water. Also called the water’s resistance to change in pH. Composed of the hydroxides, carbonates and bicarbonates in the water. One of the basic water tests necessary to determine water balance.
Alum – Any one of several aluminum compounds used in pools to form a gelatinous floc on sand filters or to coagulate and precipitate suspended particles in the water.
Ammonia – Introduced into the water by swimmers as waste (perspiration or urine) or by other means. Quickly forms foul-smelling, body- irritating chloramines – a disabled, less- effective form of chlorine. See chloramines or combined chlorine.