Pond Boss Forums Thread Like Summary - Alum Application to Reduce Phosphorus?

Late summer phytoplankton bloom from ag run off in my 8.7 ac pond in Chester County S.C.(Built 2007). Secchi disk reading 12" +/-and confirmed blue -green algae. Started treatment with running aerated well water and applying 9 gallons of Cutrine Plus to reduce algae. I have a recommendation to apply an Alum application to reduce accumulated phosphorus-but do not have any experience with Alum for phosphorus reduction.

Need help and advice as to applying Alum for this concern. Can I apply Alum in dry form? Should I dilute Alum in water and then apply in a liquid form? Should I apply Alum over a period of several weeks to reduce risk of PH drop? I understand that Alum application has risk of serious PH reduction and possible fish kill if application is too heavy!

Any help and advice will be appreciated!

Al Allison

Al:

What is your alkalinity reading of the water? If it's high then you don't have to buffer the alum as much as you do with low alkalinity water - the pH will swing quickly.

Alum should be applied as a slurry, or a liquid, not as a powder. It can be buffered by applying Hydrated lime first to strips in the pond, then go perpendicular to those strips when applying alum. You should have a bottle of pH test strips to check the pH of the water while and after applying it.

The alum works best if applied at a rate that causes P to bind and flocculate to the bottom of the pond, but again, keep an eye on the pH.

Look at the threads in the Muddy Water section, read the first 2 threads and any others that look interesting. That will give you an idea how to apply it.

Thanks for the reply. Current alkalinity is 40. 48 tons of ag lime was applied in early August. High phosphorus levels have been confirmed in water test in past months but current phosphorus levels are not known. Will test phosphorus level soon. Blue/green algae tested positive in August and paint like slime observed in shallow cove.

Applied 50 lbs of Alum in 50 gallons of water as a test. PH remained stable at 7.5. Will proceed after phosphorus test.
Thanks Al Allison

Just curious, what makes you think you need to reduce phosphorous in your body of water?

I did not see a test result. A home phosphorous test costs about the same as two fish.

Adding Cutrine to your bow will only exasperate the issue, whatever the issue is.

The thread is developing a comical direction but to Al it is a serious matter. Phosphorous is one of those things we all depend. In water, it is probably the single most important driver of primary production (with one exception, the water chemistry needed to assist its cycling). In as much as this is true, water hardness and PH, are fundamental to getting the most out of the phosphorous in our water and are important fundament parameters.

When we don't have enough phosphorous, we really need it ... but too much is one the greatest pains of pond ownership. I would say it's one of the greatest pains of pond management but that actually depends on whether the pond manager is earning a living from too much phosphorus or if the pond manager is paying for the solution. There is a difference ... where one is plagued and another blessed by the circumstance.

If Al's lake had the perfect chemistry to get the most primary production from a perfect concentration of phosphorus we wouldn't be having this conversation. We'd be talking about things like species balance and primary production utilization. We would be solving and improving the present conditions with fun stuff ... as opposed to performing this rather mundane and unpleasant task of killing primary production (making muck) and sequestering nutrients (throwing away the nutrients he paid for). I'm not making light of the task as I understand that Al wants to get his pond into a condition where he can feed again.

Once again, feed gets a pass as an underlying contributor to excessive phosphorus.