We currently have more new threads and questions related to Filamentous Algae (FA) issues than I've seen in my years on the Pond Boss Forum. In the past couple of months I've also been asked by a number of co-workers and neighbors about how to control FA. I'm hoping that we can consolidate some of the many questions/posts/suggestions into a single thread to be put in the archives.
This has been a very bad season for Filamentous Algae pond issues in much of the country. As we know all too well, much of the lower-48 has been plagued with immense precipitation, severe storms, and the consequential flooding from direct rain and from snow melt. The generally cool weather, punctuated with really hot and steamy periods, has not only made life miserable, it has exacerbated pond FA issues.
Over the years I've done much to control FA in ponds. I'm not a trained professional. This is only a serious hobby for me -- but, I've never had to resort to chemicals to control FA. I've done it mostly by mitigating nutrient inflow, and by absorbing the nutrients before they get into a pond. I've helped a number of others using similar techniques. At recent conferences, including PB-IV, I presented various techniques for mitigating unbalanced pond nutrient levels.
In the next couple of days I will try to find links to older posts about this. I'll hopefully find a way to post MS PowerPoint presentations I've prepared that relate to reducing unwanted nutrients in ponds that cause FA. Possibly a few others can point to some helpful posts regarding the control of FA.
If your FA problems are completely out of control, we have a number of great experts here on the forum who can provide excellent professional advice regarding how to deal with these issues. Please remember that some of this advice may require licensed and certified professionals.
Before you know what you are truly dealing with, please don't start indiscriminately adding dyes, chemicals, fish, etc., to your pond. Besides Pond Boss, don't forget that most states have great land-grant university Extension Service aquaculturists who can provide help at no cost.
Ken
From the very beginning 16 years ago when I built my pond the objective was to eliminate Filamentous Algae without using chemicals or dyes. The pond over those years has taken on different forms but each kind of this changing pond never had an FA problem and has never had a chemical in it. Most of the ideas that made this happen came from Andrew J Zetts of Zetts Fish Farm & Hatcheries, Drifting, PA.
The pond in the first picture is algae free and is about 2 years old. The algae fish eaters were 20 KOI, 6 Israeli carp, and 100 Channel Cats. Others were bass & bluegill.
The second picture, FA free had added as additional algae eaters were clams, craw fish and snails, and water plants which are important for FA control and supply food for marine life. At this time I also added grass carp.
The bottom picture is the pond after a winter fish kill so I am starting over with a different kind of Pond. Still FA free but no carp FA eaters and the water is very clear. The FA eliminators are lots of tadpoles, lots of water plants, and the fish I have put in so far are ones that will not create water turbidity, GSH, BG & FH. I have some bass minnows left from the winter kill.
I believe by changing the combinations of more or less plants, algae eaters and grass carp you can have a less weedy fishing pond or a more natural nature pond. But all without FA
Ok now I see you put in Israeli Carp. What exactly is an Israeli Carp and how do they differ from common carp?
Will they take over a pond?
How big do they get?
What is there diet?
Just wondering as I have access to some and wanted to know more about them before adding them to any body of water.
John, you have a beautiful pond. I don't see a fish listed as stocked that will eat any FA other than incedentally while consuming other foods. None listed are capable of digesting and extracting any nutrient value from algae. Whatever the reason your pond is FA free is great news, I just don't see any correlation between the lack of FA and fish stocked in this case.
I would suspect you have a low phosphorus inflow and a healthy plant diversity in your pond as the main factors for low algae production in you pond.
Excellent. Thanks Eric. I now remember that thread, but for some reason I couldn't find it.
MRHELLO here is a picture of an Israeli Carp.
. It is listed as a member of the mirror carp family which takes in about all carp. Zetts said it was the best algae eater of the three main ones he recommended, Israeli Carp, KOI and Channel Catfish. I have to agree since I watched my fish from a deck for hours at a time. He posted this in his Aquatic Farming Book.
"Research at Auburn University and field trials by the Soil Conservation Service has shown that Israeli Algae Eaters are very effective in controlling filamentous algae in farm ponds and reservoirs with little if any detrimental effect upon other fish. There is no worry that the Israeli will take over the pond. It is believed they will reproduce in waters that have Blue Gills or even in waters that carp have been in for any length of time because of a hormone-like repressive factor in the water."
I fed my fish everyday and I pretty much knew what I had up until the winter fish kill. I put in 6 Israeli's and 20 KOI 15 years ago and I accounted for all of them. I never had any extra Israeli or KOI so I think they were kept under control by the bass and bluegill. Zetts said he had grass carp until he saw them cleaning out bass fry and then he got rid of them. So I suppose they were helping to keep down the fry from all fish. I never saw a grass carp eat algae so I would guess it was low on their list of foods. I'm not sure you can buy Israeli carp now. I don't see any listed where I look. I estimated my Israeli were in the 10-15-20 lb range when they died. The only fish bigger were the grass carp. The Israeli carp ate FA and even made a slurping noise when eating it. Zetts said they ate one kind of algae and the KOI ate another. I do know the KOI ate FA also. My pond is 1 acre.
High turbidity and a plankton bloom. They cut off most of the light.
For FA to grow you need 3 things nutrients , water and light.
Rainman someone mentioned earlier I believe that he thought his GSH might be eating FA. Maybe I'm dreaming but I thought he cut one open and found FA in it's stomach. However I only have had 800-1000 stocked for 6 weeks so they aren't eliminating my algae. You are right, it's the plants and my pond is bermed so I don't have any inflow into my pond. Early this spring with all my algae eaters dead and before the water plants were hardly up I had FA and I thought I was in big trouble. But then came the water plants and now I don't even have a trace of FA. But there is one other thing. I had thousands of tadpole so I started to watch them closely. On my deck supporting struts and posts under water, algae was forming. The tadpoles had the structures covered while eating the algae. Now I have so many frogs with lots of bull frogs that the noise is deafening before dawn. Not only are they around the pond they are out in the spatterdock lilies. So I'm thinking of all that protein the frogs are making from bugs that will turn into fat bass in a year or two.
John, I'm not 100% sure about the Israeli carp, but Catfish and Koi do NOT eat Filamentous algae and will make no noticable impact on it whatsoever. Any FA in their stomach contents is ingested purely incidentally while eating other items....If Koi and Catfish are in a container with FA as their only food source, they will starve. They do not have stomach acid strong enough to break down the algae protein barrier and extract any nutrition from the algae...in short, they are incapable of digesting it and expend more caloric energy trying to digest FA than they can ever extract.
GSH filter panktonic algae but have little or no impact on Filamentous algae.
To my knowledge, no carp eats FA intentionally, but many have been imported and thought to do so...all have failed and caused huge problems in many areas once they escape confinement.
Israeli Carp are a "common carp" that was selectively bred as a food fish originally. If they are working for you, that is great, but I couldn't call them an "algae eater".
Rainman I respectfully have to disagree. This is my pond at age 2 with no plants to speak of for algae control. What it does have though is the algae eaters mentioned below. An open pond like this will fill rapidly with FA. This pond started to fill with FA this spring because the algae eaters were all dead from the winter fish kill. Only when the plants came up did the algae disappear. So plants or algae eaters by themselves or in combinations can eliminate FA. I can tell you that I have watched KOI and Israeli Carp eat FA hundreds of time. I have never seen a Channel Catfish eat algae because I never see them unless I feeding them with some pellets. But Zetts said they did. And I was at a pond seminar talking to a guy that used to not have FA and now did. I told him that Zetts used the three algae eaters including CC. Then he said that he had been clearing his pond of CC and that’s when his algae started. If you Google "will KOI eat algae" you will find many links saying yes.
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From the very beginning 16 years ago when I built my pond the objective was to eliminate Filamentous Algae without using chemicals or dyes. The pond over those years has taken on different forms but each kind of this changing pond never had an FA problem and has never had a chemical in it. Most of the ideas that made this happen came from Andrew J Zetts of Zetts Fish Farm & Hatcheries, Drifting, PA.
The pond in the first picture is algae free and is about 2 years old. The algae fish eaters were 20 KOI, 6 Israeli carp, and 100 Channel Cats. Others were bass & bluegill.
http://answers.yahoo.com/question/index?qid=20100404200455AAogY8qhttp://answers.yahoo.com/question/index?qid=20100105205617AA73Fifhttp://wiki.answers.com/Q/What_do_Koi_Fish_eat
That pond looks turbid to me. If so it blocks light and thus no to little FA.
ewest, why do you think the pond is turbid? I am seeing the front line on the boat going under the water, so clarity can't be to bad.
It looks to have about 12 inches of visibility in the pic. plus the color. What is the visibility?
The turbity looks like classic clay suspension. I'd wonder if the carp reproduced and are stirring up the bottom looking for food...this would also explain them eating FA...trying to eat anything to avoid starvation.
After some brief research, I found nothing at all suggesting the israeli carp eats any form of algae as a direct food source. Regardless of what any one says to the contrary...CC, lmb, grass carp nor israeli simply do not eat FA intentionally and will not control FA by consuming it (unless they are starved). None of the fish listed eat FA intentionally. with the exception of otherwise being starved, any FA they may consume would be ingested the same way a child would eat dirt after dropping a sticky sucker on the ground, picking it back up, then eating the sucker again (dirt included).
As ewest pointed out, turibidty will block the needed sunlight for any plant growth to happen...An over abundance of bottom feeders would increase the turbidity and in effect, prevent plant growth by accident, not by intentional consumption. I too would be interested in knowing what the clarity is of the water.
This breif, straight-forward and blunt article sums up the problems and misconceptions about israeli carp...
Using carp.....
I believe what you are seeing are two things. A turbidity cause by the carp and the pea green algae bloom combination. The algae bloom is the basic food source that most want and fertilize their ponds to get it when they can see beyond 18 inches in depth. The pond filled the first year and the Israeli’s, KOI, and Channel Catfish along with bass, bluegill were put in early the second year. I'm sure the fish were hungry at first during the transition and eat any FA as it tried to form. There is no FA in the picture and hasn't been for the next 15 years except for traces around the pond edges, which is a good thing. The exception that I already mentioned was between the winter fish kill and before the plants were up. The poo from the fish caused a constant green bloom from then on for food production. And some turbidity from all the carp. Then add plants, plants attract bugs, etc. and you get even more food for all pond life and a lot of fish poundage for this 1 acre pond.
This picture is a friend with a large KOI pond that has a rubber liner so there is no turbidity in this pond caused by the KOI. The pond is maybe a fifth of a acre. You can see there is a pea green algae bloom so you can hardly see the KOI. But he doesn't have any FA. Now you can attribute that to the algae bloom but not completely I think.
II like to run experiments with my pond. Can a very clear pond produce lots of fish poundage if it doesn't have a pea green algae bloom and do this naturally. I think it can. In the early 30's my aunt and uncle fished on a small river bank in Canada and caught lots of really big northern pike they had strung on a rope tied between two trees. I wish I had that picture. I assume that water was crystal clear as the waters I have ever see in Canada. So how did that food chain work? It all had to started with plants. In the 50's I used to watch a TV program where a pro fisherman would fly into upper Canada and Antarctic and catch huge fish in clear waters on nearly every cast. In the expedition of Louis and Clark and the early settlers fish were everywhere. Anyway, sorry to write a book but I find this fascinating.
John:
I have 2 small stock tanks near the house that I'm using as small ornamental ponds. One is 300 gallons, the other is 100 gallons. Both are sunk into the ground and are heated during the winter to keep them from freezing solid. They both normally have a thick photoplankton bloom, visibility varies from 6" to a foot, but it usually runs around the 6" mark. Over the years I've had FHM, Gambusia, a couple of PS, GSH and lately Blue Tilapia. All monocultures. Fish density has varied from very heavy to only 2 fish in each tank. Less fish = better visibility. But, in all cases, I have never had a FA problem in the tanks. The larger tank has a submerged filter, that has filter mesh and bio balls in it. It doesn't seem to matter if it's run or not, the visibility stays the same.
I don't attribute the lack of FA to the fish in the tank, rather I attribute it to the thick bloom that limits sunlight.
One year I had FA start in the early Spring, but as soon as the bloom started, no more FA. That was the year that I had PS in the tanks, and the water was exceptionally clear that Spring, I could see the bottom of the tanks for almost a month straight. I'm sure the PS didn't eat the FA. There are no plants in either pond.
Our pond is generally clear with clarities in the 48-120” range year around. Even when there is significant zooplankton activity (as evidenced in water sampling) the clarity remains high. The pond bottom is primarily sand and gravel with about 40% of it covered with various plant species. There are a few large 36 inch Bronze Goldfish (bronzis goldes rooti) that churn up the bottom in the shallows. The material they throw into suspension almost immediately clears as they leave an area.
When FA appears there isn’t much of it and it disappears within a week or two. Since there has been so little of it I haven’t paid much attention. Could it be that the giant natural bio filter (that the pond is) works against its development?
Not all ponds have FA. Turbidity is turbidity no matter the source. Many pond mgt books suggest to create an early season heavy plankton bloom to stop FA and use up nutrients. Thus no FA. In that case 2 of the required ingredients are missing nutrients and light. Again , as pointed out in the archives, FA needs light , nutrients and temps (which do vary by FA species)to grow. If you remove any one of the required ingredients you will not have FA. Light is the easiest to control.
Dwight, the lack of FA might be due to the large amount of water exchange going on in your pond. I see the same thing when my water mimics yours. Right now mine is stagnent (i.e. not moving much) so I'm seeing more FA along the edges.
John, your pond stocking method is an interesting concept. With complete sincerity, I'm very glad it is the way you wanted it to be, and that it has worked out very well for you.
I mean absolutely no disrespect when I say that professional pond managers worldwide get hired all the time to "correct" situations such as your pond and many (most?) pond meister's will spend vast amounts of time and money trying to eliminate common carps in their waters. Ponds with non-fertile turbidity stirred up by bottom feeders, wind/wave action or colloidal clay are generally considered very unsightly and unproductive for most.
My concern was the suggestion that some fish were able to control FA when they can't, a least through consumption. I doubt that very many people would be happy at all with a large number of fish (carp species most would consider very undesirable) muddying up their waters as a means of achieving FA or other plant control.
I am curious...could we see some pictures showing the size and coloration of your LMB and BG in the pond?
I supply my Blue Tilapia to many people with Koi ponds to control FA...that and all the research showing Koi only consume FA incidentally to ingesting other foods is another reason we need to be careful about suggesting they be used for FA control.
Hi Rainman,
I know that no disrespect was intended and I am here to learn and give observations that I find seemingly to be right but could absolutely be wrong. I have a inquiry out to a group in Israeli to an Israeli Carp club to see what kind of experiences and information they have, but their Israeli Carp do not look like what I had. So I will let you know what I hear back from them.
As you know Zetts was my guru in pond thinking since ponds were his lively hood without using chemicals for raising fish for sale. He stated that KOI were only part of the FA control and said Israeli carp and KOI eat different kinds of algae. Then he also had CC, sometimes White suckers, clams, crawfish, snails & plants. It is interesting to me about Tapia in the KOI ponds. Could the Tapia be an additional algae eater like I believe the Israeli are also along with the KOI. If I could experiment I would have a pond with no KOI, a pond next to it with KOI and see what the difference was in the FA. I can not argue that your KOI clients have FA in their ponds. That is what you do. I also have walked the edges of my pond many time and seen the KOI sucking on the trace FA.
I don't have any pictures of my bass but here is what I know. Towards the end when my fish were winter killed I had fewer bass and blue gill. The bluegill were fair sized but the bass were smaller and in the two pound range when they died and floated to the surface of the pond. I don't know the answer to this. But what I did have, and I know this sounds like fantasy for a 1 acre pond, were big CC, KOI, IC and huge GC. I attribute this to the plants and FA food and the recycled poo that kept this cycle going. I have one GC that I have see several time that survived the kill. It looks to be over 2 feet but I had many over three feet. What I suspect was happening with the bass is that the older bigger bass had died out and most of the young bass along with almost all minnows were being eaten by the big fish. I had very few minnows left. Zetts did say that he saw GC eating his bass fry and after that he got rid of all GC.
I have relatives in Rockport, TX that have a KOI pond and big homemade pond filter that impressed me.
While surfing the net I came across this post.
15 Nov 2007 06:37 PM
Originally posted by: rodrigo on 6/6/2005 7:14:00 AM
So I gill hooked a catfish on Friday and decided I'd eat him. I always enjoy opening a fish's stomach to see what they have been eating and this one blew me away. This was a fat little cat about 18" long and I suspected he'd been eating all of the little minnows which were swimming in this little pond. I was wrong. When I cut open the stomach all of this black gunk came out. When I was trying to clean off the cutting board it became clear that the gunk was algae. It's stomach was completely full.
For more background this is a small pond in the shape of a comma that is about 300 yards long from the tail to the big end and 60 yards across the big end. It's man made and fairly shallow. The fish that are caught from this pond are all stocked.
Does anyone know if algae is part of the normal diet of channel catfish? Additionally, another pond I fish has active feeding catfish that have hit poppers, which isn't normal in my book either, but some of these have had bellies filled with mud.
From and educated guess, I assume the mud could hold small crustaceans and larval insects, but if anyone can shed light on these, I'd appreciate it.
See this. Keep in mind that many fish ingest plants and FA as they forage.
http://fishbase.org/TrophicEco/FoodItems...ecies=punctatus Food I Food II Food III Food name Country Predator Stage
plants other plants benthic algae/weeds
Cladophora USA juv./adults
zoobenthos benth. crust. amphipods
Gammarus USA juv./adults
nekton finfish bony fish
Gila cypha USA juv./adults
nekton finfish bony fish
Oncorhynchus kisutch USA juv./adults
nekton finfish bony fish
Oncorhynchus mykiss USA juv./adults
nekton finfish bony fish
Oncorhynchus nerka USA juv./adults
nekton finfish bony fish
Oncorhynchus tshawytscha USA juv./adults
zoobenthos benth. crust. n.a./other benth. crustaceans
Pacifastacus leniusculus USA juv./adults
detritus detritus debris
unidentified USA juv./adults
nekton finfish n.a./other finfish
unidentified (not available) adults
plants other plants benthic algae/weeds
unidentified USA juv./adults
zoobenthos benth. crust. n.a./other benth. crustaceans
unidentified (not available) adults
zoobenthos insects insects
unidentified USA juv./adults
zoobenthos mollusks bivalves
unidentified (not available) adults
zoobenthos mollusks gastropods
unidentified (not available) adults
zoobenthos insects insects
unidentified aquatic insects USA juv./adults
others others n.a./others
unidentified terrestrial insects USA juv./adults
This is a minnow of interest to me for maintaining a clear pond but is an algae eaters that won't roil the water. Whether it can survive with bass & bluegill predators is questionable.
The Northern Redbelly Dace feeds mainly on filamentous algae and diatoms, but also zooplankton and aquatic insect larvae. Their predators consist of other fish, kingfishers and water fowl especially mergansers.[5] In small lakes where no piscivores live the Northern Redbelly Dace fills the niche of a planktivore. However in larger lakes, it is restricted to the vegetation mats by shore where it must compete with other minnows for food.
The main thing that controls weather FA grows and how much of it grows is dependant on the nutrient ratio of nitrogen and dissolved phosphorus in the water. AT times, cooler water, temperature will suppress planktonic algae and cold water FA will grow if nutrients are adequate. Nutrients in the water control plant growth.
I'm a little disappointed in my clear pond now with the algae blooms taking place underwater in some areas without an abundance of water plants. In the past I would have taken care of this with the IC, KOI and CC, but this time I don't want anything that will roil the pond's clarity. That's why I am looking at offbeat fish like the Northern Redbelly Dace that could take over when the tadpoles are grown by the third week in June. I don't think I have many options. This clear pond has been a pleasant surprise and is like looking at an aquarium to see the plants and minnows. I am spotting some plants I have never seen in my pond before because of the sunlight penetration I believe. Tilapia is out because of the winter weather kill off and I suspect they muddy the water. A long shot hope is that GSH might eat some FA as someone suggested. If anyone has any ideas let me know.
John:
I don't think they'd muddy the water (Tilapia). It would be a very interesting experiment to put some in there. The good thing is that they take care of themselves by dying in the winter so if they don't work out, you don't have to do anything to get rid of them. I have them in my pond, and the water is getting clearer, not muddier.
I put them in a .8 ac pond that historically has had a pretty bad FA problem. Nothing different has been done to the pond this year other than adding the Tilapia. The FA hasen't shown up this year. The water currently has 24" visibility, but it has a LOT of goldfish in the pond, and I think the turbidity is due to them. The goldfish have been in the pond for a few years, and even with them in the pond there was a FA problem. I have removed 274 goldfish this year all between 3" and 10" long and it seems that I haven't put a dent in their population.
esshup you have given me an option with the Blue Tilapia for next spring. Since our ponds are nearly the same size, what size and how many Blue Tilapia do you put in, and how early in the spring are they available? Do you have a good source here in IN for them? I live 75 miles south of Ft. Wayne and will most likely have to drive beyond Ft. Wayne to get mine. I would transport them in a cooler rigged with an oxygen pump to back home.
Here is a vague map of where you may find Northern Redbelly Dace close to Indiana.
http://quod.lib.umich.edu/f/fish4ic/x-46/phoeos
If you expect northern redbelly dace to do well in a pond, it had better stay cool, as in darn near trout temperature cool, it better be heavily vegetated, on the soft side and if it has LMB in it, don't expect them to last long...
I put in 15# this year, and will probably put in 20# nest year. My sourse for Blue Tilapia is R&S Tilapia Stockers, in Missouri. Rex Rains, AKA Rainman on here. He delivers. I got mine the 2nd week of May.
CJB I have the vegetation part covered for the survival of the northern redbelly dace but I do have LMB that are in the minnow stage. The dace bright colors would probably be their downfall with the LMB present as I never had any small KOI grow up to join the 20 large ones I had. The dace might survive the Indiana water temps. When I was in Minnesota’s BWCA lake area 50 miles from Lake Superior during a September I took baths in the lakes and the water was bath tub warm which really surprised me. According to the Michigan dace map they are only 150 miles north of me so temperature wise they might have a chance here in e. central IN. However I found a paper where northern redbelly dace were introduced in Ohio and didn't take. There was no information on why they didn't survive.
Thanks for the information essup.
Right now my algae free pond has FA rather bad in places out to about 20 feet from the edges of the pond. The plant vegetation does it's part in the control of FA but it can't do it all. When I had the algae eating fish this didn't happen in my 16 years of ponding. If it wasn't for wanting a very clear pond I would do what worked before, 6 Israeli Carp, 20 KOI and ended up with about 30 CC for 1 acre. The problem with this is, since Zetts went out of business in Dritings, PA I don't think you can buy Israeli Carp anywhere in the US. My large tadpole population kept the pond completely free of FA until they turned into frogs and that's when the FA bloom started. So I am considering two options now. Tilapia and Northern redbelly dace minnows, both algae eaters. Tilapia would have to be replaced every year because they won't survive the winters and the dace are cold natured and may not survive the warm weather and bass predators. It was believed there were no Northern redbelly dace in Indiana but I think I have found where they just might be in the Mongo, IN area. So I am thinking of doing a kayak overnighter into the area before fall and see what I can find. My secret map.
http://www.michigandnr.com/PUBLICATIONS/PDFS/ifr/ifrlibra/Special/Reports/sr24.pdf
With all the FA we are having now I went back to the Farmland Conservation Club to check out what I call the mystery pond. An FA free pond, and her FA chocked sister pond that is much closer together then I had realized, maybe as close as 500 feet.
I have kept tabs of the mystery pond now for over 10 years and there has never been any FA on it. I originally thought the reason was because it used to have thousands of black ramshorn snail in it but only found a few yesterday. Here are yesterdays pictures.
SISTER POND
MYSTERY POND
SNAILS FROM MYSTERY POND
Are there any fish in the mystery pond? If so, what?
any difference in water temps between the two ponds?
I have never seen any fish in the Mystery pond. I always thought the snails might have been the reason for the FA absence but now I don't see many ramshorn snails so I think I have to rule that out. I did see some things dart from under a rock. I think were probably crawfish but seemed to small. I will check again when I go back and I will check the water temperatures and ph of both ponds. The past president of the Farmland Conservation Club thought the pond was more turbid then in the past and might be from some digging at the tail end for expansion. I thought the pond was more turbid then as I remember and visibility looked to be maybe 18".
Temperature and PH results for the sister pond and the mystery pond.
Sister Pond: 80 degrees--PH 8.4+ off my chart,,, complete FA & Water Mill coverage.
MYSTERY POND: 86 degrees--PH 7.2 no vegetation at all except cattails around the edges.
The pond is more turbid then in past years and that may account for the much lower population of black ramshorn snail.
Visibility is about a foot. I'll see if I can get permission to put a baited minnow trap in the pond and see what might be in there that may account for no plant life or FA.
Interesting comparative situation on our two ponds this year. Upper pond received initial fert treatment on schedule. Lower pond did not. And it got too clear, and had a terrible outbreak of FA. Finally got the fert program going in May, got a good plankton bloom, and the FA died back over a period of a few weeks. The FA is not completely gone, but it's probably 80% gone. The bloom blocked the light and apparently killed the FA. The upper pond, which was fertilized early, has maintained a good bloom and had no FA issues. Based on this experience I certainly agree with the view that controlling sunlight penetration is an effective way to control FA. That's my nickel cause I'm outta pennies.