Pond Boss Forums INTRO Questions & Observations What should I know about alum treatments for algae

Hearing more and more about aluminum sulfate for algae, is anyone an expert here?

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I'm not an expert in algae control, but I think aluminum sulfate or "alum" is used to clear ponds by attaching to suspended sediments and bringing them to the bottom of the pond. Copper sulfate is commonly used for algae control. I'm sure someone will chime in here...

Sue is right. Alum is for turbidity reduction not algae control.

http://srac.tamu.edu/tmppdfs/144249-460f...bd2bb6a27c452c2


Aquatic weed control

http://srac.tamu.edu/tmppdfs/144249-SRAC...bd2bb6a27c452c2

Not necessarily. Alum can be used to tie up phosphates in the sediment so they can't be used for algae and macrophyte production. There should be information if you do an Internet search.

Cecil while alum and gypsum can tie up phosphorus I would never bet on it reducing algae (FA).There are several problems with that approach. One it can also clear the water letting more sun get to the FA causing an algae explosion. Two the phosphorous removed into the floc which settles out is carried down to the FA growing on the bottom. Three you have to know your water chemistry (what limiting factor N,P,K or other is present) and how much of your P is removed (tied up) by the alum. If alum is tried and your guess on any of the points is wrong you can easily be much worse off than before especially in low alkalinity waters.

There are much better options for FA control than alum not to mention the difficulty of use and cost.

Respectfully yes and no. If you can tie up the phosphate AND stop new phosphate from coming in... Wish I had more time to debate this with you. As far as the cost I found alum cheaper than any herbicide from my local chemical supply.

I assume using bacterial control at the bottom will help to break down any flocculated nutrients that end up there? Also, the pond has been heavily dyed (per landowner request) which I hope would help with sunlight problems. I am trying to overcome the FA in a pond that hasnt responded to my to date "blind" swings at it with copper (sulfate & chelated), endothol, and diquat. Have since purchased water quality equip. hindsight is 20/20 isnt it.

JMAC how big is the pond , how deep , what is the alkalinity and how much water under 6 ft.? Also without the dye how are your visibilities? I assume there are fish in the pond that you want to keep. Have you had the water and soil tested ?

I agree with Erik on this one. With over 25 year water treatment experience, I would not ever see alum being used for biological control. While it is true that some of ortho-phosphate may be tied up and removed as a solid by the use of alum, the mechanism of disociation creates AlOH precipitate that in turn, ties up solids though flocculation. This reduces the alkalinity, reduces suspended solids, and "clears up" turbidity. The water will likely still have sufficient phophorus to sustain biological activity, including filamentous algae, particularly since sunlight penetration will be enhanced. Keep in mind that the phosphorus precipitated will soon be redissolved into solution through biological processes in the water. If you want to see a prolific FA growth, look at an ditch receiving a constant well stream sometime. Even though the water is nutrient poor, it supports a healthy FA growth due to the clarity of the water. My belief is that FA growth is more directly dependent on water clarity than any other factor.

O.K. I stand corrected.

Pond is 2.5 Acres, 6 feet deep avg. Clarity is 3-4ft w/o dye. Testing equip was purchased to start looking at chems in spring. Anyone have any advice on a good start for the spring to get ahead of the FA. I am using floridone (Sonar AS) for weeds. Thanks for the info all!

Check the label I think sonar use is recommended only when water temps are above 50 F. There are lots of threads here on control of FA (filamentous algae). The search function will find them for you. A history of the pond would help with recommendations. Where is the fertility (nutrients)coming from.

Right on the sonar, we wait until the 50 degree mark in the spring. Most nutrients are allochtanous... Lawn fertilizers. Lots of accumulation of leaves etc. on the bottom. But I've never had such a stubborn pond. Just need a majic combo of chems, bacteria, aeration i think

You can start with the Archive thread on FA.

My understanding was that the phosphates tied up by the alum were permanently unavailable for future plant use. Aluminum phosphate is a fairly stable entity, isn't it? M Spinhirne seems to be indicating that the AlPh will be "redissolved" into soln. through biological processes. What processes are we talking about?

It appears that it is soluble but not absorbable in many animals but is by plants especially in water where it is broken down by biologic processes.

"Although it is unstable to heat, in geologically stable regions like Australia and Southern Africa, alumiunium phosphate is generally the most common form of phosphorus in soils, as it forms when phosphate in rainwater reacts with dissolved aluminium in the soil. Although it is not as insoluble as many other components of soils in those regions, aluminium phosphate can form exceedingly insoluble double salts known as taranakites with many essential elements for plant growth that are normally highly soluble in water, such as potassium and nitrogen."

More on the subject.

Because alum is acidic, it has effects in ad-

dition to coagulation. Alum reacts in water as

follows:

Al•(SO4)• + 6H•O-• 2AI(OH)•

+ 6H I+ + 3SO4 :•-

Some of the aluminum ions react with any col-

loidal clay particles present; the rest precipitate

out as aluminum hydroxide, AI(OH)• (below

pH 6, more aluminum hydroxide is soluble).

Some hydrogen ions also react with colloids, but

most neutralize carbonate and bicarbonate to

reduce total alkalinity and depress pH. The

drop in pH is greater in waters with lower initial

amounts of total alkalinity, as illustrated in Fig.

2. In the absence of other chemicals, 1 rag/liter

of alum theoretically destroys 0.5 rag/liter of

total alkalinity.



In this study, the toxicity of alum to fathead

minnows decreased with increasing total alka-

linity (Table 2). All fish mortalities occurred

during the first 12 hours of the 96-hour tests.

Although pH values were driven as low as 4.41

in these tests, acidity probably was not the cause

of death. Mount (1973) found that fathead

minnows could survive pH 4.5 indefinitely and

Swingle (1961) reported the acid death point

for pond fish as 4.0. Death of fathead minnows

in the present study was likely related to high

concentrations of aluminum ion in waters of

low pH rather than to the direct effect of low

pH. At pH 4.4, the concentration of aluminum

ion in equilibrium with AI(OH)s is approxi-

mately 1.7 mg/liter. Hydrated lime essentially

negated the influence of alum on total alkalin-

ity, pH, and fish mortality .



Data reported by McKee and Wolf (1963)

and findings reported in Tables 2, 3, and 4 in-

dicate that alum treatments of 10 to 30 mg/liter

will not be harmful to fish except in water with

low total alkalinity. For example, treatment of

water with an initial total alkalinity of 12 mg/

liter with 30 mg/liter of alum wouldestroy all

of the alkalinity, reduce the pH, and probably

kill fish.



Sources of positive

electrolytes which are commonly employed for

turbidity removal are aluminum sulfate (alum),

ferric sulfate, calcium hydroxide (hydrated

lime), and calcium sulfate (gypsum). Their po-

tential for removing turbidity from ponds has

not been adequately evaluated (Martin 1978),

so the present study was conducted.





Alum precipitates phosphorus as insoluble

aluminum phosphate (Sawyer and McCarty

1967), so applications of alum have been used

to reduce phosphorus concentrations and phy-

toplankton productivity in natural waters (Pe-

terson et al. 1973; Bandow 1974). However, the

species of aluminum resulting from alum treat-

ment quickly disappear from solution if treated

water contains residual alkalinity (Stumm and

Morgan 1970). Thus, applications of alum to

remove clay turbidity will not adversely affect

the availability of phosphorus added in fertil-

izer later in the growing season. In unfertilized

ponds, alum treatment will lead to lowered

phosphorus concentrations and plankton pro-

duction.



Hydrated lime may be ap-

plied simultaneously at the rate of 0.40 mg/liter

per 1.0 mg/liter of alum to prevent unfavorable

changes in alkalinity and pH. For maximum

coagulation of colloidal particles, water should

contain residual alkalinity after alum treatment

(Sawyer and McCarty 1967), so hydrated lime

application is beneficial in soft water even when

alum toxicity to fish is of no concern.



One of the other articles stated that while Alum precipitates phosphorus it leaves a good amount of phosphorus intact and available for use. Where pH levels are low the acidity makes for a higher degree of the Alum phosphate re-soluble. As per Mike's comments clear water plus residual phosphorus and re-soluble nutrients at the FA level in low alkalinity waters may cause a FA explosion. A better method may be lime (or high alkalinity) and a good plankton bloom to shade out the FA.

Howbout a treatment plan with bacteria, flocculant, dye, and algaecide?