Algae, Copper Sulfate & Alkalinity

Herbicides for Algae

• Copper sulfate – inexpensive (chelated copper?)

• Endothal (Hydrothol) – some toxicity to fish

• Sodium Carbonate Peroxyhydrate(Green Clean, et.al.)

Copper

Photosynthesis Inhibitor

pH

• pH indicates whether water is acid, neutral or base

• A range of 6.5 to 9.0 is desired for aquatic life

Fig. 2. pH scale showing recommended range (Wurts & Durborow, 1992).

A pH of 7 is neutral, pH < 7 is acidic , pH > 7 is basic (alkaline).

0

4.0

7

9.0 11

14

6.5

pH

Death DeathDesired range for

aquaculture

Alkalinity

• Measures how much base is present in water

• Must be above 20 ppm to use copper sulfate

• Can be increased with liming

Alkalinity & pH

• Low pH is common with low alkalinity

• Increasing alkalinity increases pH

• Alkalinity stabilizes pH

Changes in pH during a 24-hour period in waters of high and

low total alkalinities (Wurts and Durborow, 1992).

pH

High alkalinity water

Low alkalinity water

11 -

10 -

9 -

8 -

7 -

6 -

5 -

Early

Morning

Early

Morning

Late

Afternoon

Usual Recommendation

• For algae in a “farm pond”

• 1.0 ppm Copper Sulfate

• 2.75 lb/acre-foot

• What about fish?

Copper Toxicity

• Copper is toxic to fish

• Low pH increases toxicity

• Low alkalinity prolongs toxicity

Liming

• Adding ag. limestone will increase pH & alkalinity

• Collect soil samples from pond bottom, to a depth of 6 inches

• Send samples to soil testing lab

• Use recommendation for “Alfalfa”

Ponds with Water

• Collect water sample

• Test for total alkalinity

• If total alkalinity is < 20 mg/L, pond should be limed

• Some swimming pool test kits measure alkalinity

Benefits of Liming

• Helps prevent wide swings in pH

• Enhances effect of fertilization

• Adds Ca & Mg to water

• Improves safety for using copper

Copper & Alkalinity

• Cu2SO4 in water = 2Cu+2 + SO4-4

• CaCO3 in water = Ca+2 + CO3-2

• MgCO3 in water = Mg+2 + CO3-2

Copper & Alkalinity

• High alkalinity reduces effectiveness of copper

• Low alkalinity prolongs copper toxicity

• Copper treatments must be adjusted for alkalinity

Warning: Avoid Using

• Hydrated & Quick (Slaked & Burnt) Lime

• These compounds can cause sudden, large increases in pH

• Rapid pH changes can kill fish

Applying Copper

• Pillow case – “the classic”

• Trash can and siphon hose

• Criss-cross the entire pond

Spot Treatments

• Large floating mats of algae & low alkalinity

• Supersaturated solution

• Hand sprayer

Full Pond Treatments

• Use total dose for the whole pond

• Algae have no roots, leaves, stems

• Do not treat if algal coverage is more than 25-30 % -- may cause oxygen depletion

• Do not reduce dose by 2/3 or 3/4

Aquatic Food Chain

• Phytoplankton

• Zooplankton

• Small Insects

• Small Fish (minnows & bluegills)

• Large Fish (bass & catfish)

Aquatic Weeds

Filamentous AlgaeMoss, Pond Scum

Bluegreen Algae

Chara(an alga)

Duckweed

Watermeal

Southern Naiad

Water Primrose

Variable Leaf Pondweed

Spatterdock(Water lily)

Cattail

Willow

Look Alikes

1

2

3

Look Alike ID

1. Coontail

2. Slender or Spiney-Leaf Naiad

3. Chara

Pond Call Questions

• How big – acres?

• How deep?

• Extensive shallow areas?

• Livestock grazing/watering?

• Cropland/fertilizers/turf strip?

Slide Shows On-line www.ca.uky.edu/wkrec/WurtsPrespage.htm

On-line Literaturewww.ca.uky.edu/wkrec/WurtsLitpage.htm

ExtensionAquacultureSpecialist

Dr. Bill WurtsKentucky StateUniversity CEP