Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Phosphorous Binders - aluminum sulfate vs. natural

So, I think I want to apply a phosphorous binder due to my algae issues and lab tests:

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=569653#Post569653
https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=570968#Post570968

I searched the forum and found mostly old arguments about Phoslock.

My understanding is that aluminum sulfate is a traditional, low-cost approach. The downside is that it can dangerously lower pH. However, my pH (8.3) and total alkalinity (180 ppm) are on the high side, so maybe I have enough buffer?

There seems to be many products for natural, non-alum, binders. Phoslock, MetaFloc, AirMax Ecoboost, etc. These are more pricey.

Thoughts on these products?

Also, when is the best time to apply a "reset" dosage of phosphorous binder? Now (Fall) or early next Spring? Right now, the undesirable grasses/cattails are dead, and I raked out all the floating mats of FA.

I think having a good understanding of when applying a phosphorus binder would really benefit a pond would be a valuable tool on the forum!

There have been several threads in the past, but I don't think we have compiled enough "experimental" results into one place to draw a lot of useful conclusions. I can't remember exactly who was in the few good threads we did have, and who helps manage enough ponds to know.

You might add Fire Is Hot or esshup in the Display Name box for your searches?

Good luck on your pond improvements!

The best time to apply the binder for us up here is right after ice out when all the plants and the majority of phytoplankton has died and decomposed. That puts the highest amount of soluble P in the water. You really, really should apply enough so that the binder create flocculation. That way the P precipitates out and falls to the bottom of the pond.

Read the alum kicks clays butt threads. That gives you an idea how to apply it. Have some way to pond test water pH during application. Rex usually says 300# of alum and 150# of hydrated lime per acre foot of water. Too long of a process to re-type it here - look in the clearing turbid clay laden ponds for how to apply it. You cannot mix the two together and apply at the same time. Think of making Jello......

Thanks. I read through some of those alum threads. I have 5.5 acre-ft of volume. That's 2500 lbs of alum and lime to acquire, haul, mix, and apply. That's well beyond my capability. Seems a lot easier to spray a few gallons of MetaFloc, which includes flocculation.

My water is very clear, not muddy. No clay turbidity. Just elevated phosphorous.

I would be VERY interested in seeing water test results from pre application and comparing it to post application. SRP and TP readings pre/post.

I'm watching too. I'm very interested in that phosphate binder too. Let us know how it goes.
Thanks
Dave

In early March 2025, Helena and SePro initiated work with Texas Parks & Wildlife biologists on a “case study” to technically and empirically document the effects of EutraSORB G, EutroSORB WC and EutroSORB SI on a 5 surface-acre city park pond in Katy, TX (Mary Jo Peckham Park).
The park’s pond is occupied (“infested” 😉) by a relative high population of waterfowl, which do what waterfowl do best when fed ample amounts of foodstuffs by the visiting public.
In 2023 & 2024, the park’s pond experienced several bouts of excessive planktonic algae blooms; often accompanied by Cyanobacteria blooms that posed a threat to both “wildlife” and park-visiting pets.
The objective of the case study is to document effects, benefits and economics entailed with a properly executed phosphorus mitigation program.
Lanthanum (a rare earth element) is the key component found in EutroSORB G (10% granular formulation), EutroSorb WC (liquid) and Phoslock (5% granular formulation). Use-rates for each product’s formulation are properly based upon phosphorus sample results rather than a predesignated rate per acre-foot. Accordingly, the formulation(s) and dosage(s) for this case study will be based upon collected water and benthic soil samples, which are currently undergoing analysis within SePro’s water-quality testing lab.
The final results of this case study will become available this fall after the treatment(s) have concluded and several post-treatment water/soil samples are analyzed.
Personally, I believe this case study will provide an excellent comparison to innumerable private ponds that suffer from the effects of excessive & long term eutrophication.
I’m happy to share the case study results (later this year) with anyone who expresses an interest.

Thanks Kelly that's great information. There has been aot of discussion but I haven't seen much for real world data. Thank you for you help on this.
Dave

There are several case studies on the use of lanthanum for phosphorus mitigation but they mostly pertain to large water bodies; often involving potable public water sources. That’s a high-volume market (funded by OPM 😉) that manufacturers likely (IMO) find more efficient to monetize. In contrast, the private pond market is highly fractured and challenging to educate on the concept’s merits, but is cumulatively huge.
So far, my experiences with lanthanum products (and the feedback from commercial applicators) is generally positive WHEN the product is properly and adequately deployed.
Those who own/maintain a swimming pool might be familiar with various “phosphate removers”. Guess what substance most of those products contain. Lol!

Kelly:

I am very interested in the results. Please either e-mail them to me. I'll ping you towards the end of the season to see how things are progressing. The constant addition of excess P will be an issue but I bet you guys will take that into consideration.

I now have some results. However, the pre/post measurements are 6 months apart and from different labs, so that throws in some additional variables.

Oct 11, 2024 - Pond water analysis by Natural Waterscapes
Orthophosphate = 0.06 mg/L

April 1, 2025 - I applied 3.5 gallons of MetaFloc to my 5.5 acre-ft pond per the label dosage recommendation

Aril 22, 2025 - Water test at a local laboratory
Orthophosphate = 0.004 mg/L

So, that is a significant improvement. Plus, there is very little FA in the pond right now. A year ago at this time, there was a good amount.

Thank you!

Send a sample out to be tested that was collected the 10th-12th of October 2025 to compare. Different amounts of plant and phytoplankton life in the pond will also change amounts of Orthophosphate.

Metafloc is being featured heavily on youtube and facebook so this seems like a good time to bump this thread.

I'm curious because they are promoting putting $150,000 of it in at once to "reset" a pond. I know it's a proprietary blend of "natural" substances but I can't help suspect the primary ingredients are alum and blue food dye.

Metafloc is an almost clear liquid so I doubt there is any blue dye in it

It may have blued up a bit since your experience with it.

I may be overly suspicious as on the product page they explicitly say it does not contain "aluminum or lanthanum compounds."

I still suspect they are misleading with how they advertise it.

It's a blend of different ingredients and they often talk about one of the ingredients and imply it's the primary agent without actually saying it. So when they say it's a "biological phosphorus removal product" I suspect they are saying it contains biologicals in addition to some other, probably much more active, chemical ingredient. Indeed at one point they say

"MetaFloc works best in water temperatures above 50°F when bacterial activity is optimal. It can still provide phosphorus binding through the flocculant component in colder water, but the biological activity that provides long-term sediment control is reduced below 40°F. For best results, apply during the growing season."

After the "reset" application of MetaFloc in April, I applied several "maintenance" dosages of Ecoboost throughout the summer:

https://www.thepondguy.com/product/airmax-ecoboost/

October 8, 2025 - Water test at a local laboratory
Orthophosphate = 0.003 mg/L

So, the very low orthophosphate (FRP) level appears to have been constant all season long. However, I still had a curly leaf pondweed explosion in spring (killed off nicely with fluridone), and another heavy FA growth in late summer. The FA was not as bad as last year, but enough that I have been raking it out for a couple weeks, now.

Given all this, my conclusion is phosphorous is not causing the plant growth in my pond, and I am questioning the need to keep applying pricey chemicals.

Ditto - if we can find the results of the study from Mr. Duffie it would help all of us understand how to battle nutrient load, phosphorous accumulation, and also figure out why weeks explode when there isn't phosphorous to blame as well.

P in water grows plankton/algae. P in the pond bottom grows vascular plants even if the P in the water is low. So, both water and sediment should be tested. Where the sunlight can reach the bottom of the pond, the plants will grow. (and most likely algae too).

P in water grows plankton/algae. P in the pond bottom grows vascular plants even if the P in the water is low. So, both water and sediment should be tested. Where the sunlight can reach the bottom of the pond, the plants will grow. (and most likely algae too).

Don't know much about aquatic plants but think about what pops up in little cracks in your driveway. If you have light and water it's real tough to stop plants from growing.

We're pulling the final water and sediment samples from the Katy (TX) park pond tomorrow (Tues/17th).
Honestly, i haven't seen any dramatic changes so far - visibly. Then again, this particular pond was likely the worse possible place to test a P-binder other than perhaps a hog farm collection-basis.

On a second note, we're now looking into doing some aquatic field studies with humic acid products. Preliminary studies in controlled environments were very promising. Details to follow.

Thanks Kelly! Good to see you checking in.

Thanks Kelly.

We still learn good science from "negative" results.

I hope you keep pursuing this project. We get lots of questions every spring and summer about excess plant and algae growth in people's ponds.

Thanks Kelly. The more we know the better.

It is best, in so far as possible, to identify the limiting factor or factors in pond water or soils, before spending a bunch of $ on an unknown course of action.

B.Cody - also appreciates the updates from Kelly Duffie. THANK YOU!