How Does an Alum Application Affect Fish and Plants?

Aluminum is considered a non-essential metal because fish and other aquatic life do not need it to function. There is a large body of scientific literature documenting the safe use of alum in lake environment conditions, which has allowed the North American
Lake Management Society to fully endorse its use (NALMS, 2017).

Is Alum Safe?

Alum has been repeatedly shown to be safe for humans. Alum is a common
food additive and has also been used for decades to clean our drinking
water before consumption. HAB uses the exact same drinking water certified
alum when preforming a lake improvement application.

What is Alum and How Does it Work?

Alum (aluminum sulfate) is a nontoxic liquid that
is commonly used in water treatment plants to
clarify drinking water. It’s use in lakes began in
the early 1970’s and is used to reduce the amount
of phosphorus in the water. Lower amounts of phosphorus lead to lower amounts of algae and the symptoms associated with poor water quality. Alum is most often used to control phosphorus release from the lake bottom sediments (internal loading). Research has shown that even when external sources of phosphorus from the surrounding watershed are lowered, the internal cycling can continue to support signi cant nuisance algal blooms.

Where Does All of This Phosphorus Come From?

Phosphorus enters lakes from two sources. Phosphorus entering the lake from outside sources are called external sources. These sources originate in the watershed and are either directly rinsed into the lake or flow to a stream that enters the lake. Common external sources include lawn fertilizers, septic systems, agricultural practices, stormwater, soil erosion and geese: anything that causes phosphorus to enter the lake from the watershed.
Once the external source of phosphorus enters the lake, it is deposited in the lakebed and is recycled back into the water column. This is the second source of phosphorus and it originates from within the lake itself. This is called an internal source and these inputs are most common during the summer
and winter when water oxygen concentrations are low or zero near the bottom. This condition causes changes in the chemistry of the lakebed that lead to the phosphorus leaching out of the sediment and into the water.