Controlling green scum in stock tanks

              Controlling Green Scum
in Stock Tanks
Green scum, or slime, that builds up in livestock
drinking troughs and tanks is algae. It cannot grow
without sunlight, but putting covers on tanks is not
practical on New Mexico farms and ranches.
Copper sulfate, often called bluestone, will kill the
algae for a period of several months. It is cheap, costing less than $2 a pound at most drugstores. When
used in the correct amounts, it is not harmful to fish
or animals.
In troughs or small tanks, a safe dosage is one level
teaspoonful of copper sulfate per 1500 gallons of
water. One ounce will treat 8000 gallons of water.
A simple way to treat troughs and small tanks is to
dissolve the proper amount of copper sulfate in a
glass or enamelware container, and stir the solution
slowly into the trough water. Where the algae buildup
is excessive, pour the solution directly on the scum
on the walls of the trough or tank to speed up the kill.
In treating large stock tanks or ponds, drag a sack
containing the correct amount of copper sulfate behind a boat, pacing yourself to cover the heavily infested areas first and working out to deeper water.
Proper concentrations are one to three pounds per
acre-foot of volume, but since most people tend to
over-estimate the volume, one pound per acre-foot is
a safer treatment.
If your tank contains catfish (not scaled fish), treat
one-half of the pond at a time, and allow the fish to
move to untreated water. Scaled fish are less sensitive.
The drawings and formulas show how to estimate
the approximate number of cubic feet in troughs and
tanks of different sizes. Measure in feet and decimals
of feet rather than in feet and inches, to keep your
calculations simple.
You can figure the number of gallons in a tank by
multiplying the number of cubic feet by 7.48, the
number of gallons in one cubic foot. Other useful
conversions are:
1 acre-foot = 43,560 cubic feet or 325,800 gallons
1 gallon = 231 cubic inches
Formulas for Estimating Volumes in Small Tanks
Volume in
cubic feet
(3.14) (D) (D) (g)
When D = diameter in feet
£ = length in feet
V»-b--»/
Volume in  =     (a)  (b)  (8)
cubic feet 2
When a = depth in feet
b = width in feet
£ = length in feet
Volume in
cubic feet
(3.14)  (D)  (D)  (£)
4
When D = diameter in feet
C   = depth in feet
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