Algae Control

I. 2 types of algae that affect ponds in this area:

A. Filamentous - String Algae

1. Short String - beneficial, gives pond natural look
2. Long String - most troublesome

B. Unicellular - makes water murky (pea soup)

II. Causes

A. High nutrient levels in water

1. Too many fish
2. Over feeding fish
3. Plant soils too high in organic matter
4. Runoffs into pond (lawn fertilizer)
5. Too much sunlight

III. Control - Goal is to control, not eradicate, some algae is beneficial

A. Reduce nutrient levels

1. Add more submerged plants - anacharis, cabomba
2. Add more floating plants - water hyacinth, cress, lettuce
3. Feed fish less
4. Reduce fish volume
5. Plant plants in soils with low organic matter

B. Increase nitrifying bacteria

1. Add bacteria
2. Increase sites for bacteria to colonize

a. Bio-Filter
b. Gravel in pond

3. Adjust water for ideal bacteria growing conditions

a. 6.6 - 7.8 pH
b. Chlorine free water
c. Dissolved Oxygen above 5ppm

C. Shade 1/3 of surface area

1. Add floating plants
2. Add black dye (most effective in still water)

D. Creatures

1. Japanese black snails (great for string algae control)

a. 1 snail/s.f. surface area

2. Fish

a. Koi

1) Must be careful, may also eat good plants

b. Goldfish
c. 'Pleco' Catfish

1) Ugly, but eat a lot
2) Don't survive winters

d. Israeli Carp

1) Get too big (best for large earth bottom ponds)
2) Prolific breeders

E. Chemical

1. Pond Balance (Brand Name)

a. Effective against string algae
b. May take 3 applications 2 weeks apart

2. Cu Sulfate

a. Effective on string algae
b. Higher rates could kill snails
c. Plants safe
d. Rate
33 ppm on alternate days over 2 week period
(fish safe)

3. Simazine

a. .5 mg/L
b. Fish safe
c. Kills snails
d. Remove plants

4. Barley Straw

a. Mesh bag filled with barley straw
b. Remove from water before decomposes
c. Reputed to be effective against string algae

F. Recommendations

If your pond has a Bio-Filter, unicellular algae is probably not a problem. The only time it will be noticeable is in the early spring. The spring algae bloom should last only a few weeks, until the water temperature increases enough for the bacteria to start working.

To control the string algae, we first recommend adding Japanese black snails, then possibly more fish and lastly a chemical product. Pond Balance is a relatively new product but shows lots of promise and doesn't have the negatives that most other chemicals do.