Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Filamentous Algae

I need some expert advice on controlling unwanted algae and weeds! I have two types of weed problems going on currently. The first is Sago pondweed or at least that's what the guy i sent samples to tells me. It's only a problem in spots around the pond although even though it's a rooted plant it somehow seems to come loose and gather in huge clumps and float around top water making fishing nearly impossible in some areas! The REAL problem i'm dealing with is Filamentous algae. In the last week we've had temperatures of 94 degrees and just over night i have nasty neon green bloom covering 3/4 of my pond. VERY aggrivating! The aggrivating part is that I run a Vertex bottom diffuser systems in my pond 24/7. I have 10 grass carp stocked on my 3/4 acre pond. I have added beneficial bacteria, i keep pond dye in it and even try to rake the floating mats out when they blow to one side of the pond (which seems to be highly ineffective!) To really rub salt in my wound the pond about 200 feet across from mine that has zero areation , no maintenance and is just a natural farm pond is crystal clear and very fishable??? Go figure?? Can someone give me any ideas what to do? I realize i can use a copper product and kill it , sink it to the bottom and wait for it to rebloom all over again but i'm looking for a real fix...possibly a way to get rid of all these nutrients or find a product that keeps this thing in control before it ever has a chance to get out of hand! I have pond completely stocked and would love to fish, however there isnt a clear spot on my pond to cast so i'm assuming fishing this year is over until late fall. Thanks in advance for someone who can help with this aggrivating problem!!

What is the average depth of your pond? What brand of pond dye are you using? How much dye have you applied and how often are you re-applying it? Have you had similar problems in past years? Is there a known nutrient source that is getting into your pond like lawn fertilizers, ag fertilizer or possible septic leak? It is possible to have a water test done and to find out what your nutrient levels are like. If the test indicates your phosphorous levels are high there are a couple of products on the market that can be applied that will bind to the phosphorous and make it unusable for the algae and pondweeds but if you are getting a constant flow of nutrients every time you get rain it may not give you much long term control. How long ago were the grass carp stocked? You can use several products for control of the sago pondweed. My personal favorite has been aquathol K (liquid or pellets) but weedtrine and Reward should also work fine.

Thanks for quick response. Average depth probably around 4-5 feet. I've tried different types of dye. I'm currently using Pond Logic Nature's blue, and I've used aquashade in the past.I'm applying it every few months or so. There were known nutrients of cow manure getting in pond in past but nothing in last year or more. I had a similar algae bloom last year but thought I would be in better shape this year with upgraded areation and beneficial bacteria but no change at all. I'd love to have a water test done...where do I send it? If i had a product that could bind the nutrients I think that might do it. I don't have a constant flow that I'm aware of. I'm not even worrying about the Sago pondweed right now because the Filamentous algae is out of control so bad that It's literally smothering the pond weed out!

I also wanted to note green head that I put 600lbs of Alum in pond last year which helped some I suppose but I have it stocked with Fish now and not sure if that's safe. Plus i'm really tired of spending money on this thing...a pond is way more expensive habit that I would have ever dreamed!

It might be possible that the sago pondweed is providing a shallow substrate upon which the filamentous algae is growing. Algae can, and will grow on submerged plants that are contacted by sunlight.
Unless you've identified that algae is indeed growing on the pond's bottom and then rising to the surface as it matures, my guess is that the sago is providing an artificial "bottom" for the algea's proliferation.
If so, then your efforts should focus on controlling the sago. I'm surprised the grass carp aren't doing their part. Might be that they need some help to get ahead of the sago's growth-curve (ie. knock it back in selected areas with a contact-herbicide, such a REWARD, KOMEEN, NAUTIQUE, etc).

Two pictures of my same pond without FA and never a chemical in it, but managed two different ways. The first picture is about 12 years ago with no FA, but with the much needed green bloom, which you need for the food chain and oxygen. The nitrates from the fish produced the green bloom enough that I didn't have to fertilize. The green bloom also helps limit sunlight for weed control. My algae eaters for one acre were 20 KOI, 6 Israeli, and Channel Catfish along with 18 grass carp (too Many) for weed control. The algae eaters produced babies for the predicators to grow fat on. The other stocked fish were bass & bluegill. This pond is very fishable.


This second picture is now. FA is controlled with water plants mostly and tadpoles. The water has no green bloom but is very clear down to 6 feet. I am still experimenting with this pond.

Those lily like plants are spatterdock. In time with gradually clearing water, they will cause you problems - too many, too deep.

FA growing on various submerged vascular plants (epiphytic) indicates there is an excess of nutrients that are not being used by the vascular plants. Normally FA only grows when where is an excess of unused nutrients. When natural waters are balanced in terms of water quality and plants (vegetation) very little FA grows. Notice amount of FA in many better quality larger lakes.

belkins456 to my knowledge there should be no problem with the alum that was applied last year. The only problem associated with alum applications that I'm aware of is the potential for a rapid pH change shortly after the application that could be lethal to the fish. Usually the alum application is done with sodium bicarbonate to offset the pH change. The other products I have seen in the past that are advertised to reduce phos. levels have alum and sodium bicarbonate as the ingredients. In my limited experience with them I have seen application rates for alum to be anywhere from 50lbs per acre foot to 150lbs per acre foot as determined by lab analysis. Kelly makes a great point with the algae growing on top of the pondweeds as I too have seen this happen. I have had a couple of ponds with significant amounts of algae growing on the coontail and once the coontail was dead the algae was greatly reduced. To my knowledge Aquashade was the only aquatic dye labeled by the EPA as an aquatic growth inhibitor so thats what I use and recommend. To get the full potential of the dye it should be applied early and fairly often. The recommended application rate is 1 gal per 4 acre feet of water. For my initial applition I like use 1.5-2times the recommended rate in the spring and follow up with the labeled rate every 4-6 weeks, depending on rainfall amounts, throughout the growing season and I have had quite a bit of success with control in water greater than 2ft deep. Even with the dye I do still see some algae and pondweeds growing around the edges in the 1-2ft deep range. Regarding the grass carp, the biologist recommended rate for control here in IL is 5 per surface acre for most situation but if your grass carp are older than 7 years old I have read that they may not be as effective at controlling growth. I dont remember where I've read or heard that so it may be an old wives tale that someone can clear up for us. For the water test I have used aquatic control and the test you would want would be the turbidity/nutrient analysis if you think the phos. levels are going to be high and if you are interested in having them figure out how much alum and sodium bicarbonate to apply. I believe the cost is somewhere between $85-100 for the test.

I appreciate all the information and I plan on adding a Gallon of Aquashade tommorrow, although since i'm in "full bloom" i'm not expecting much from this. I believe we are at the conclusion I have excess nutrients in my pond causing the algae to grow, so now i've just got to get a straight answer on how to remove them? I don't think algae growing on top of pond weeds is my problem as only about 10 percent of the pond has a weed problem and 90 percent has algae problem today. My grass carp have only been in pond for 2 months now and are only 12-14" long so i'm not expecting much from them yet. I figure next season hopefully theyll make a difference with weeds possibly but since they don't eat filamentous algae I don't look for them to solve that issue. So is alum pretty much my only option to get rid of this stuff? What about some of these algaecides? Does anyone even recommend a copper product such as Cutrine or something of that nature? Or is this just the band aid approach? Looking forward to more answers. Thanks.

I just read about a product called Phoslock in the aquatic control newsletter. It is not alum based but "a lanthanum modified clay" that binds to free reactive phosphorous. Here is a quote from the newsletter. "Treating a typical one acre pond that is 4 foot deep with 2.5 pails (40 pound pails) of Phoslock will remove 80 ppb of phosphourous from the pond. This is significant because 80ppb of phosphorous provides enough fuel to creat 400lbs of algae in that same pond." They go on to say a nutrient test is recommended to determine the necessary amount to remove the phosphorous from the pond.
Regarding the current algae problem...raking is always a better fix than using chemicals as you are eliminating the nutrient cycling you get from the chemical treatments but it is obviously more work. I do like cutrine for algae but it is a band aid. If you can treat it chemically and you maintain the shade of the dye and you have the bacteria and aeration system you might be able to minimize the regrowth. Otherwise it is sometimes necessary to repeat cutrine applications every 2-6 weeks depending on the severity of the problem. if you dont physically remove the algae with 90% percent coverage it would probably be recommended to treat no more than half of the pond, wait 10-14 days and then treat the other half.

I found that just the other day surfing the net for Algae solutions...

Interesting quote from their website:

Treatment with Phoslock provides a “reset” of the ecological clock of the water body. That is, it returns the water body to the phosphorus level which is likely to have existed many years prior to the events which have given rise to the increased levels.

Management strategies limit additional nutrients finding their way into the water body. However, it is rarely possible to prevent nutrients building up as there are various sources including runoff and waste from birds and animals. Phoslock may remain active and capture phosphorus from natural sources for many years.

I'm researching this Phoslock product as it sounds interesting. I'll let you know if i go with it. I'm wondering how affordable it is? I may just go the chemical route since it's so bad and try to keep it in check and hit it with an attack plan early next season. Raking it out at this point is out of the question unless I had a crew of 20 men armed with rakes and spent 10 hours or more. The pond is almost completely covered at this point and it's pretty thick. Thanks for all your help.

I haven't seen anything regarding the costs yet. Try contacting Aquatic Control and see what they say. I'm not sure who else carries it yet. Also, GreenClean is a non copper based algaecide that actually puts oxygen in the water as it destroys algae so it could reduce the chance of a fish kill. GreenClean begins destroying algae almost as soon as its applied. I have only sampled small areas and have not tried treating a fully covered pond. Hopefully someone can jump in with advice if you are interested in trying it. The application rate is up to 90lbs per acre foot of water and the approx costs I have seen are just under $200 per 50lbs bag.

Do not kill an extensive coverage of algae all at once or all that decay of dead algae will consume enough DO (oxygen) that loss of oxygen will kill fish - maybe all fish esp if you get a few cloudy days. Larger fish will die first. Presence of blue dye will reduce the ability of the pond to naturally produce dissolved oxygen via phytoplakton which increases the chance of a DO shortage if lots of FA is decaying. Lots of decaying algae will release lots of bound nutrients to 'feed' more plant growth of some sort. Consider using a seine to skim off large amounts of algae before treating. Removing algae reduces the absorbed nutrients.

In rereading this whole topic and since your 3/4 pond is an ave depthof 4-5ft IMO your long term plans should budget for renovating and rebuilding this pond to have deeper ave depths and minimize watershed nutrient accumulation. As you are learning shallow water usually results in production of more plants of some kind.

I spoke with Aquatic Control today about the Phoslock product and I think it definately may be an option down the road. For now I went back to the old method of just spraying Cutrine Plus. I have my pond algae free after spraying 1.5 gallons across the entire pond. So far nothing has started to bloom back but I have another gallon on hand to spot treat it until I get a permanent solution. One plus was the Cutrine even killed my Sago pond weed or at least burnt it badly to a crisp brown. At this point it has solved all of my problems. The guy at Aquatic Control told me it was perfectly acceptable to spot treat the entire season with the Cutrine product as a long term solution but I'd still like to try to bind the nutrients so rebloom wouldnt happen as often if possible.

I think I might try the Phoslock (thank you green head for posting about this). I have a newly re-dug, 1/4 surface acre pond (3:1 slope, 13' deep) that had quite a bit of FA upon filling. All is good now since I've started my bottom aerator so I probably won't use it this year but I think it's a great (safe) way to reduce nutrients in a pond.

Here is some info on Phoslock: http://www.phoslock.com.au/faqs-usa.php#2

It's available here: https://www.lakelawnandpond.com/MiscContactUs.aspx

I was told my pond would need one pail, 40 lbs ($175, free shipping). You have to remove or kill your algae first. I agree with Bill about increasing the depth and controlling watershed though or you may end up battling this problem often.

By removing the P you are adding a limiting factor to the natural system. What happens when the limiting factor is removed ? If there is no P then only a very limited food chain of plankton can exist to feed your system/fish. BTW the most often encountered factor causing ponds to have low productivity is low P.

Ewest- So what do you recommend to control the filamentous algae then? Is my method of just using Cutrine Plus as a year long solution acceptable?

See this from the archives. The best way is to have a plankton bloom early enough to shade out light to the bottom where the FA forms.

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