Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Vegetation Management - Suppress Filamentous Algae

The forum receives lots of questions about unwanted plants. Both from new members, and from long-time pond owners. There are certainly many hypereutrophic (very high concentration of nutrients) ponds in the U.S. that are literally choked with a variety of lush plants filling nearly all of the available space.

However, my reading suggests that filamentous algae is public enemy #1.

Further, I have seen several articles and knowledgeable posters suggest that adding beneficial submerged, emergent, or floating plants can sequester away nutrients, therefore making them unavailable to the FA.

Unfortunately, I have never seen any type of quantitative analysis of results, nor read a post on Pond Boss where someone reported vanquishing their FA by using competing photosynthesizers.

If any of the members would like to contribute ideas and observations, I think it would be very handy to create a template for new pond designs to combat/suppress FA in regions where it is highly likely that FA will become a problem as the pond matures.


Idea #1
Is there a recommended submerged plant that tends to establish fairly readily, yet is very susceptible to pond herbicide control? Especially a type of plant or growth habit that is net beneficial to the totality of the various fish species in the pond? (This may be dependent upon the specific "fish" goals of the pond.)

I believe that it would be very advantageous to have such a plant that would steal nutrients from the FA, but could be easily cleared using spot herbicide treatments as needed for "fishable" areas, family recreation areas, etc.


Idea #2
Do NOT introduce triploid grass carp during the initial/early stocking of the pond.

I believe that TGC will eat limited amounts of some types of algae, and perhaps a bit FA, but usually only after they have already eliminated most of the vegetation they prefer in their diet. Therefore, the state agency recommendations to stock TGC actually shift the balance away from beneficial plants to MORE filamentous algae in the pond. This seems very counter-productive in my non-expert opinion.

(I suspect the same would hold true for initially stocking crayfish in the pond.)


Idea #3
Are there any submerged, emergent, or floating plants that are easy to harvest and REMOVE from the pond?

We always mention the importance of removing FA from the pond watershed after it has been laboriously raked out - to keep those nutrients from going back into the pond and replenishing the FA growth cycle.

It sure would be nice to have some plants that could take up nutrients all year from a eutrophic pond, and then those sequestered nutrients could be permanently removed from the water column by harvesting the plants.


Idea #4
If people can't easily harvest the plant matter, can we use other creatures to perform the harvest?

After the beneficial plants are WELL established, would that be a good time to add TGC or crayfish to consume large amounts of plant matter? If you knew that you would perform electro-surveys in the future, it would be convenient to perhaps overstock TGC and then remove them (and all of those nutrients) after a few years.

Likewise, it would be convenient if you could establish a sustainable population of crayfish in a bass-rich pond. I would think the plant nutrients would eventually wind up in the bellies of the bass, and then would be removed through angling. And that it would also be tough for the crayfish to denude established plants when there are bass easily hunting crayfish as their hiding cover decreases.

[Obviously, tilapia are the best method of "creature" assistance in controlling FA. If you are a new pond owner reading this thread, check to see if tilapia are allowed in your state. If they are permitted, then I recommend you go through the archives and read some of the excellent tilapia threads.]


Idea #5
Create a bog filter to either catch nutrients introduced via incoming surface water, or to support a large population of plants to sequester nutrients away from the FA.

When building a new pond where the core trench in the dam is the main "seal" for the pond, it would not add very much expense at all to remove a foot or two of top soil at the upper end of the pond to a create a large shallow area where the plants could be easily establish in the remaining topsoil. It would be even more beneficial if that bog area was in the downwind direction of the prevailing spring/summer winds. Windy days could push pond water into the bog, and the hopefully nutrient depleted water would then return to the main water column during calmer days.

This idea is to add LOTS of emergent plants to the total pond area. Perhaps mildly spreading plants that ONLY thrive in shallow water would make this approach net beneficial? You certainly would need to avoid plants that easily propagate by seed dispersal or even dispersal by bits of the body of the plants.

[Or is this a terrible idea because deliberately creating a large area of shallow water is just going to provide additional bottom substrate to initiate the growth of FA?]

I did get a few responses to a tangential post on a related topic here.

Are Nutrients Well-Mixed?


Idea #6
Excavating the maximum safe/stable slopes from the pond edge to create a deeper pond bottom is generally the best "design" to suppress FA.

Are there any pond design features that make aeration or pond dyeing easier or more efficient?

If you are going to have to rake FA in your pond, are there any features you could add prior to pond filling that would make that task easier?




Please feel free to add any better ideas to this thread. Also, post any big "wins" or "losses" you have observed on this topic from your own ponds.



P.S. I have made many assumptions above. Please correct any erroneous assumptions, or add any needed clarifications to simplified assumptions.

Fisingrod:

Local lake, in the early Spring has Curly Leaf Pondweed growing out to about 8' water depth. Water clarity is about 6'. Once that dies back in late June, the boat traffic keeps the FA broken up but planktonic algae grows and drops water clarity to 18" or less. Last year they had a Cyanobacteria bloom in late August........

esshup,

Thanks for the input, but your post is at least three levels above my knowledge base. (I generally become more educated when learning things about 1-2 levels above my current knowledge.)

I believe Curly Leaf Pondweed is considered an invasive species in many states? Therefore you are posting a cautionary tale?

It sounds like it ALMOST fits my criteria of a submerged plant that sequesters the nutrients away from the FA. Unlike most of our other pond plants, it generally grows very early in colder waters, right when the FA is also starting.

However, it grows so quickly that it can become a matted obstruction itself in the pond. And then it dies off so rapidly in the summer that it dumps a bunch of dead organic matter in the pond water column that can either resort in fish kills and/or fuels late season growth of undesirable plants/organisms such as the Cyanobacteria bloom?

I assume the native Pondweed varieties would be much better in your area where you get to observe the life cycle of lots of ponds?

The CLPW IS an invasive and isn't recommended for ponds, although because of Canada Geese I battle it in a few ponds. It was used as an example of vascular pond weed sequestering enough nutrients to eliminate algae, either planktonic or string algae.

I don't know of any non-invasive pond weed that would sequester enough nutrients to make as large of a water quality change.

When sending water out for testing, and you want to know the levels of nutrients in the water do it in January/February when the majority of plants and algae are NOT growing. Typically the nutrients that would be sequestered in the plants/algae are in the water column. But due to the cold water temps most plants/algae won't be actively growing. I have seen some FA grow under the ice and in my pond I have seen it get to be 3'-4' long when in the water flow of the winter diffuser. I believe it was Spirogyra.

Thanks for that additional reply, esshup.

Lots of valuable information there for owners wanting to make improvement to their ponds!