Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Seine for removing algae?

Since ice-off, dead mats of algae have been rising to the surface - filamentous and/or chara. I am really pissed off about this since I applied phosphorous binders all last season, measured low orthophosphates, and still had a big bloom of FA in the late summer. I raked out a good amount. I am raking again this spring, and it is tedious. Plus the rake misses some clumps.

Does anybody use a seine to more thoroughly and more quickly remove FA? I am thinking to home-brew something out of orange safety/snow fence. I am not sure if this sinks. May need some weights or leadcore rope.

https://www.amazon.com/dp/B08FHLWQ33/ref=twister_B0G58ZL1RW?_encoding=UTF8&th=1

That's a good idea. I would take that idea a step further. If you are going to use that multiple times a year, you have to think about storage. A seine works by the top of it floating on the surface, and the bottom either dragging on the bottom or hanging down in the water column like a shower curtain. There is a rope on the top of it and a rope on the bottom of it to pull it through the water in the pond.

The snow fence is a good idea but it will need modifying.

If you are concentrating on the floating algae, cut that fence so it's only 2' tall. Thread a Polypropylene rope through the top of the seine. I say thread because if you zip tie it to the rope you have to rely on the strength of the zip ties to hold the net to the rope. Polypropylene rope because it floats. You will also have to either thread the rope through floats or find a way to clip floats to the rope to keep that end of the seine floating. Floats

You will have to weigh the bottom of the net so it is vertical in the water column. Again use a rope on the bottom, but this time I'd use a braided nylon rope. You will have to weigh the bottom rope. Enough weight to get it to sink, not too much weight so it sinks the whole thing including the floats. Net Leads Or you could use a weighted rope like this: Weighted rope

I would extend the rope anywhere from a few feet to 30+ feet from the end of the netting. That will give you something to hold onto when you put it into the pond, and pull it to the shore. You want to pull the bottom of the net slightly ahead of the top of the net so it doesn't ride up and over the FA.

Encircle the FA mats. Pull to shore, use a rake to get them out of the pond. They may be too heavy to pull out of the pond with the snow fence seine.

Or if that sounds like too much work to build it, call a net company like Memphis, Nichols, etc. to have them make you a strong short seine. I'd think you would want mesh that was 3/4"-1" . Get it coated as the new will last a LOT longer. You will have to lay it out on the grass to dry before rolling it up and putting it away or it will rot. You won't have that problem with the snow fence.

Knobber, how big is your pond?

Can you do it from shore with ropes and two people? (Or you plus wife on ATV, etc.?)

The whole pond might be too heavy of a load to drag onto shore, so maybe make your "seine" only a 1/2-pond-width long?

P.S. I wonder how much of those mats grew last year and stayed on the bottom before your P-binder started to effect your water chemistry. Are you going to try it one more year to check the longer term results?

Yeah. The more I thought about it, the more I realized that it needs to mimic a real seine with floats on top and weight on bottom. Thanks for the info.

The pond perimeter is about 700 feet. I am thinking a much shorter seine length, like 25 feet at a time. Me at one end, and my son on the other. The algae is really heavy. Snow fence is cheap, so I can experiment.

I wasn't planning on another round of P-binder. This was the outcome. Seemingly very low orthophosphate all season long, yet plenty of algae. Now I am questioning the lab results. Disheartening.

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

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

Summer 2025 - I applied several "maintenance" dosages of Ecoboost

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

Knobber. Plants are very efficient at scavenging phosphorus from the water column. While the number .06 mg/L may be a high number (where more frequently one may test much lower numbers) ... that amount of phosphorus in the water column isn't a very high amount. There are around 6.774 million liters of water in 5.5 acre-feet. And so there are 406,438 mg of phosphorus at the first test. This equates to .406 kg of orthophosphate in the entire pond. around 0.44 lbs/acre.

Based on your description of weeds crops, there is much more than that weight of phosphorus in the pond ... but not in the water column. Biological action on sediments releases phosphorous, nitrogen, and other important nutrients including CO2. This happens throughout out the year and much more than .44 lbs/acre of phosphorous are being recycled annually. It is just as the pond weeds grow ... they metabolize and use the phosphorous. IOWs they consume it and sequester it in their living tissue. This is why the treatments are not removing all that much phosphorous from your pond.

I don't know how much active ingredient is in 3.5 gallons of Meta-floc. But I do question the weight of phosphate the active ingredients can make bio-unavailable to your pond plants. I don't think it is near enough to make a big impact. Now removing the living plants to decay outside the drainage of your pond would have a much larger effect provided you removed a sufficient weight of them. A decent rule of thumb is .4-1 lb of phosphorus for each 100 lbs of dry matter you remove. An interesting exercise that could help a lot of members is good measurement of your removal of plants and associated effects to guage the effectiveness of nutrient removal by this method. You wouldn't need to measure the dry weight of all but if you could track the volume of the drained but wet weed removed you could dry a small sample to get a conversion factor for your methods of removal. That dry sample could be tested for nutrients (just like hay) if you wanted to track the nutrients removed each season. If you remove 10 tons of weed that have 1 ton of dry matter that contain 0.8 lbs of phosphorus per 100 lbs ... then you would remove 16 lbs of phosphorus or 8 lbs of phosphorus per acre.

Let's say that a ton of dry weight weed were removed in 2026. This would remove 16 lbs of phosphorus from the nutrient pool. But it is important to note that the effect you will see will be no more than 10 lbs reduction of annual phosphorus mobilization in 2027. This is because only a little over 60% of the nutrients will be recycled in 2027. Each year the effect of removing weeds in 2026 will decline. For example, in 2028, expect 3.6 lbs of phosphorus reduction in that year's mobilization of phosphorus. The point here is that you will need to maintain removal each year where after 5 years the full benefit will be seen (which will be a reduction of 16 lbs of phosphorus annually per ton of dry matter removed --- this of course depends on the phosphorus content of the dry weed --- here assumed to be 0.8 lbs per 100 weight).

Other considerations ...

There are other sources of nutrients that will accumulate in the pond each year. For example, atmospheric deposition of nitrogen and phosphorus ... organic deposits brought in from rain ... deposits from avian visitors ... deposition by wind of things like grass cuttings and leaves ... and finally ... the deposition that you can effectively control ... feed and/or fertilizer. All of these sources are new annual inputs of nutrients and so if one is removing living plants as a means of nutrient control ... it should at least match the input to keep conditions the same and exceed it to improve conditions.

Just a FYI, I haven't had "feel good" test results when using different labs. One lab where the water test was over $200 showed the results as 0. Upon further research, I found out that the levels that I needed to test down to was too small of an amount so it was below their detection threshold. My fault, I went on a recommendation and didn't research it myself. I have a lab that I use now that I have repeatable "feel good" results from.

Another thing to take into consideration is that plants and algae sequester P. Meaning that if nothing was applied to the water and the initial test was taken in January, and the 2nd test was taken in late August, there would be less P in the water because P was sequestered in the growing plants and algae. Even the amount of phytoplankton in the pond might make a difference.

When I take water samples for testing, when doing nutrient abatement, I'll take a water sample pre-application and about 5 days post application and send them both to the same lab at the same time. When doing general water quality testing I will try to collect samples from a particular pond at the same time of year. Take a secchi reading and note if any herbicides or algaecides were applied recently, and if yes, exactly when they were applied, how much was used and what was used.

The safety fence does indeed float.

I made a 10-ft long x 2-ft tall prototype seine to test the flotation. On the bottom is 1/8" wire rope I had laying around around from another project. On the top is floating polypropylene rope with 1 foot sections of a pool noodle. This seems to float nicely and hang vertically in the water column.

Next, I will make a 50-ft long version for the algae collection.

Knobber - How well did it work for for removing the floating algae? Can you post a picture of the results of FA in your DYI seine?

Knobber, that looks great! Please let us know how well it works!

Knobber,

As you said above, snow fence is cheap. If you end up pulling with a vehicle, you might have enough force to tear a few strands of fence.

If you haven't built the full-scale algae seine yet, perhaps consider a double-layer of snow fence? That way when the first layer tries to stretch and tear, the second layer should help spread the force a little bit.


Filamentous algae delenda est!

So, I tried my contraption today. 40 feet long, single ply of the snow fence. I deployed the seine from a rowboat, which was a little difficult by myself in the wind. The floatation and orientation is really good - hangs nice and vertical.

The wife and I each took an end and pulled it in to shore. Not too difficult. The seine does a great job of gathering up everything in its path. This is unlike tossing a rake, which sheds vortices from the ends as you retrieve it, and chunks of algae swirl away.

Now the hard part begins - rake out the algae, load it on the yard glider, and unload it far away. Then, extract the seine from the mess and repeat many times. At least I don't have to put on my waders for this job.

Attached are the before and after photos.

Excellent work Knobber!

Some additional thoughts to mitigate that last bit of HARD work:

Can you attach the ropes to a vehicle (truck, ATV, tractor, etc.) and pull the seine ashore so the FA can start drying?

Can you wade into the pond and clip a rope to the bottom of your seine (at the bisection of the arc) and pull the FA ashore by curling up the bottom of the net?

Do you have "easy" control of the water level of your pond? For example, if you draw it down 1.5', will it fill back to normal pool elevation with the next rain? If so, would lowering your water level make for easier work getting that mass of FA onto the shore?

(Since I don't have eyeballs on the actual scene, I suspect there are flaws in my ideas. However, hopefully you can improve on them and come up with a solution that saves you AND some other PB readers some future back-breaking labor.)

Thanks FishinRod. You have good ideas. I like the bisection rope.

At the moment, I am dumping the algae in the woods over the hill and out of the watershed, so I can't drag the seine to the final resting spot. I don't really want to dry the mats on shore, as it takes forever and is unsightly. I subscribe to the "pick it up only once" theory, so raking the collection from shallow water straight on to the tow vehicle seems to work. I may change my mind as this job progresses, though!

The main advantage of the seine is more thorough collection and confinement of the algae. This, however, leads to more mass to get rid of! Ugh!

Agreed.

That is one of the easiest ways to tell rookies from experts on dirt moving jobs. Or any type of construction work, for that matter!


I am really liking your post and the accompanying pictures. I plan on linking it in the future when we get questions from new pond owners regarding getting rid of their FA.

That worked well, good job!!

Jpsdad

You are talking my language but my vocabulary is limited. I am very interested in listing and semi-quantifying all of the nutrient inputs and nutrient harvesting in my pond. You mentioned a rule of thumb range for Phosphorus dry weight percent. Where did you get this? It is very difficult to find this kind of information without getting lost in AI circles referencing vendor advertisements! My pond is about 1/4 acre in a wooded rural area filled by groundwater and occasional runoff from non-agricultural properties, and is bordered all around with 20-50 ft of wetlands vegetation. I believe the major source of nutrients to be leaf fall. The only nutrient losses are any vegetation I harvest and any fish (I hope!) that are caught. Is that P content good for dry leaves? What would you use for fish harvesting? It is a new pond(4yr). It sat idle for those four years and has already accumulated leaf muck which I am working to remove by perimeter raking, diffuser aeration, and aerobic bacteria treatments. The bacteria treatments, however just release nutrients back into the water and have resulted in a major duckweed bloom. I am setting up a duckweed skimmer using a 2” semi trash pump and dewatering bags. This seems like a necessary follow on activity to get rid of muck and extract phosphorus, as duckweed is said to be rich in Phosphorus. Is Duckweed within the range of you rule of thumb? Have I missed anything?

Knobber - What you have with this FA removal thread so far I think is Really GREAT work so far for your DIY algae removal project. Earlier in the thread by 'jpsdad' noted in phosphorus removal post is I think very important for dealing with and determining phosphorus content in filamentous algae and FA control using non-chemical, and more natural nutrient management in ponds.

I put this thread in the Pond Boss Common Pond Q & A archives of: Filamentous Algae, aka Pond Scum/Moss - Management

I am happy to report that I finally have filamentous algae under control. I threw the kitchen sink at it this summer:

Early May: I seined out the mats of algae over a period of weeks as noted in the earlier posts. Continued pond dye every 8 weeks.

End of May: stocked Tilapia

June-July: Heavy algae mats reappeared, and I pummeled them with max-strength Cutrine Plus treatments. I used a 16 gallon electric sprayer in the back of my UTV. (Big difference over hand pump sprayers.) Lots of dead algae sank to the bottom.

Started applying muck pellets every two weeks.

Water tests revealed total phosphorous < 10 micro-g/L and free reactive phosphorous < 5 micro-g/L. Both values are pretty low.

I splurged for sediment fractionation testing. Potentially releasable phosphorous = 208 mg/kg. Apatite and residual = 127 mg/kg. After consulting with the testing service and ChatGPT, I opted to do nothing about locking up this phosphorous, since things were looking up.

A healthy shoreline buffer developed with various rushes, arrowhead, some catttails, and pickerel weed (planted by me.)

Some algae continued to form, but it was sparse and easily dispersed with wind and rain (and tilapia?)

August: Started applying Airmax Pond Clear every two weeks (All-natural bacterial cleaner plus EcoBoost PRx flocculant).

End of August: The pond looks the best it has in 4 years. Almost no FA, and some chara here and there.

I am going to guess that the Tilapia made the biggest impact, but it took 8-10 weeks to see the difference. Maybe last year's phosphorous treatments kicked in as well.

I think I need to keep up this rigorous maintenance routine every year.

The fight results are in: Knobber 1, FA 0!

Well done, Knobber.

Stay tuned for the rematch.

Knobber - Removing as many tilapia as possible in September also removes nutrients for next years crop of algae. The planted plants should spread and grow better next year and beyond to help compete with the growth of excess algae.

Question - What type of sample did you have to send for the sediment fractionation testing? And what company did the testing?

I have yet to catch a Tilapia on hook and line, and usually the SMB or YP get to the bait first. The Tilapia gobble up any and all sizes of feed (including Endurance 22mm pellets), such that I stopped feeding for a while. Since I stopped pellet feeding, I noticed every speck of FA is just about gone.

My next attempt at bait will be to tie up a couple 5mm pellets in a mesh, similar to a spawn bag. If that fails, I heard that Tilapia will struggle at the surface in cooler Fall water temps and can be scooped up.

A bottom sample was taken from about 10 feet of water with an Ekman Dredge and sent to SePro for analysis.

For catching fish that love pellets, use a Stubby Steve's or Berkley Power Egg for bait and chum with pellets.

Method courtesy of George Glazener.