I live in Idaho and have posted last year in the new member section. I have an acre pond that is spring fed. The water is 58 degrees. It does not freeze in the winter. I have trout in the pond as well as grass carp. My problem is the filamentous algae, which has gotten worse this winter. We have had a cold winter with temps down to -20 degrees but the algae continues to grow. It is worse now than it was last summer. Should I drain first this spring and start brand new or treat. With what would be recommended.

The algae needs nutrients to thrive. Where does it come from?

Like Dave said you need to know where the nutrients is coming from. if you have acess to a boat you could put a large pond rake on the back and just rake the algae but it wouldn't be a peremanat fix you could try pond dye but if you have a good amount of flow coming into and out of your pond that could get expensive in a hurry. btw thanks guys i wouldn't know what i do without this site.

Louis, like others have said, you need to figure out where the nutrients are coming from. Be more concerned with Phosphorous than with Nitrogen, but look for both.

Algacides that have copper in them could be deadly to trout. With that said, I've used chelated copper products in my pond in small amounts (treating a 20 square foot area in an acre pond) with no ill effects when I had trout in it.

A Sodium Carbonate Peroxyhydrate based algaecide is safe to use with trout in the water, but like any herbacide, you have to watch that you don't kill too much at once, because when it decays it needs O2. The decaying matter will win when when it comes to who gets more O2, it or the fish.............

Louis, I expect that the dying algae is contributing to your nutrient load. Once it gets started, it pretty well feeds on itself. Spraying a heavy infestation only contributes more nutrients as it dies.

I know nothing about cold water algae or it's survival. With it being spring fed, can you even drain it?

Hopefully Kelly Duffie will see this and chime in.

If it is a FA type it is probably "spirogyra" as we have it growing well in waters med- high in ortho P and N at temps as low as 42-50F range and often under clear ice.Consider getting a water sample to a lab such as AquaFix www.naturalake.com to see what your nutrient load is. Then perhaps a bacterial program such as using VitaStim Polar may help your situation.I would concentrate on the cause vs the result (symptom)a picture may help also.

On your grass carp. If your grass carp are more than 3 years old you may want to look into removing them later and putting younger grass carp in now. Grass carp will eat up to 100% of their weight for the first couple of years. After they reach 10# they tend to drop eating to around 25% of their weight. Also note that as water temps decline the grass carp slow in their eating. This would mean it may be more productive to add some grass carp now and then remove some of the older ones nearer to summer when the water temps get higher.

Thank you all for your comments. I have tried Cutrine plus last summer and only used sporadically with excellent results but only had a minimal amount of the algae then. The algae is filamentous and slimy and comes to the surface. I should have kept up with usage of Cutrine but it went wild this winter. Not sure where the nutrients are coming from; could be from fallen leaves from this fall. I tried to remove as much as possible as it fell into the pond. The water comes directly from a spring that travels through a buried 10 inch corrugated pipe that I placed several years ago and I don't believe nutrients are coming from spring. The pond depth average is about 6 feet with the deepest part being about 12-14 feet. The flow is about 60-80 gallons/minute. The grass carp are old now, about 4 years and are quite large. Good thought about adding young smaller ones but will they consume this type of algae. I also have aerators in place that are constant. Not sure how to attach picture but will try. My thinking is to drain pond and dry out the algae. Do you think that would help? Any help would be appreciated.

draining the pond will work a local lake "somerset lake" used to be drained every few years to kill the algae but if i was you id rake the dried stuff up so it doesn't come back so quick. but you dont want to drain all the water just leave a few feet of it to keep the fish alive also with that kind of spring flow youl need to use a siphon to drain the pond and keep it low.

I have a head gate to shut the spring flow to the pond and have another head gate that I can open to drain the pond. It never drains completely so the fish can still survive. I went to the website suggested (AquaFix) and found the product Pondzilla 100. Maybe I should use this after the pond starts to fill again. Has anybody tried that product?

Greetings Louis:

Most comments here suggest that excess nutrients are causing your filamentous algae problem. I agree that nutrients can be an issue however I also believe that some filamentous algae is normal, natural, and beneficial.

I believe that your nutrient problem is made worse by the fact that you have grass carp in the pond. Grass carp recycle nutrients very fast as the plant material they eat goes through their digestive system. (Similar to Canadian Geese here in Ohio). Here is an article that will confirm my comments.
http://ohioline.osu.edu/a-fact/pdf/0019.pdf

You appear to have an infestation. I have not found any single tool that corrects an infestation.

So, the question is how to attack an infestation with no winter die back. Carp can't do it even though they will eat it when there is nothing else available.

Cutrine Plus will kill it but the dying plants add nutrients for new growth. Since the water is a constant 58 degrees, tilapia might be able to help after spraying.

If it were me, and it's not, I would consider a draw down, spraying of the remainder and a heckuva infusion of tilapia. Are tilapia legal in Idaho?

You know, maybe it is a coincidence, but the algae started getting worse about 2 yrs after I got the grass carp. There are about 20 or so very large ones now (about 12-15 lbs). Will plan to remove them and clean any dead algae after I drain. Will spray with the Cutrine plus. Don't know about the Tilapia - will have to look into that. Thanks for all the input. That will help me get started and hopefully I can get a handle on this.

From above:

I believe that your nutrient problem is made worse by the fact that you have grass carp in the pond. Grass carp recycle nutrients very fast as the plant material they eat goes through their digestive system. (Similar to Canadian Geese here in Ohio). Here is an article that will confirm my comments.
http://ohioline.osu.edu/a-fact/pdf/0019.pdf

P.S. Louis, draining your pond is no guarantee against re-infestation from FA algae. There are many, many, "spores" left behind that you will never be able to eliminate 100%. I would purchase a bag of Cutrine Granules and spread them over the pond before the FA algae floats to the top. Controlling the FA algae early on the bottom of the pond where it begins it's lifecycle is the key. After you use the Cutrine Granules, you then may want to think about adding a gallon of Aquashade.....(note: it is important to wait about 2 weeks after you treat the pond with the Cutrine Granules before you add the Aquashade.

I would NOT replace any of the amur in the pond for the above reasons mentioned.

I don't think tilapia are an option for you since they do not survive well in water below 64F and 58F is even more detrimental to them. Be wise with the application of Cutrine even the granules. High doses in relatively soft water can kill trout. I would treat sections of the pond at a time. With maybe a week or two between applications. Cutrine has the ability to remain active in the water column. Length of active time depends on several factors. So you don't want to retreat with residual Cutrine (copper) in the water column. Trout are the most sensitive to copper compared to about all freshwater fish. You may have to periodically drain the pond and dredge out organically nutrient rich sediments to suppress the FA growth in the not too far future. You are experiencing a common problem in a pond that receives lots of fish feed applications and higher fish production.

Your correct about the Tilapia. I contacted Tilapia stockers and they said my pond water was too cold. Am planning to drain this spring. Thanks everyone.

Louis, I'm glad you got my reply and I should have added in your email that tilapia are not legal for open water stocking in Idaho.

Welcome to the forum!

louis I forgot to mention that somerset lake is drained in the fall and filled in the spring I gues there logic is to freeze the algae to help prevent the it from growing back but it seems to work.

small pond, what roots are you referring to?

sorry essup it was late and i wasn't thinking right don't know why i typed that. algae doesn't even have roots. but when they would let every thing freeze the algae didn't seem to come back as fast. no more late night posting for me.