Permaculture solution to watermeal infested pond?

Hi all, first post but long time reader.

I have about a 1/2 acre pond, about 8 - 9 ft deep at deepest spots, which is completely covered in watermeal (some duckweed, but not much).

Here is some info:
The pond doesn't have any aeration, and no wave action to speak of.
Trees lines the edges (don't know all species) and I assume alot of leaves fall into/have fallen into the pond
Trees block much wind, but every so often the wind blows the watermeal to one side, clearing up the surface

I'm new to this pond, but looking at satellite photos show it being "green" with what I assume is watermeal, every summer.

There are some who say tilapia fish consume watermeal. Unfortunately, I am in zone 5a/b so the water temperature won't support them very well.

The only other solution I have seen offered is an herbicide (Sonar, Avast, Whitecap). I'd rather not use a chemical treatment if I can help it!

Any ideas on how to approach this from a permaculture view?
Thanks!

One webpage suggests Koi will eat watermeal. 

http://ohioline.osu.edu/a-fact/0014.html

H Ludi Tyler wrote:
One webpage suggests Koi will eat watermeal.   

http://ohioline.osu.edu/a-fact/0014.html

H,

Thanks!

One issue I note is that, even on this page, they recommend wiping out the watermeal first with an herbicide and then using preventative measure (aeration, koi stocking).

They mention that koi can't control an infested site, but stocking them in spring to control it might work. I'm not sure if they mean stocking a pond that doesn't have any watermeal in the first place and the koi keep it OUT or if them mean the koi in spring can keep the watermeal from coming BACK. Watermeal is the quintessential perennial. It goes dormant and sinks to the bottom during fall and winter and then floats back up in spring.

hi Joseph,
first, what do want to do with the pond, fish?, swim?, irrigation?, just look pretty?
from a permie perspective:

watermeal and duckweed are not evil
from what you say and the webpage Ludi posted says, your pond has been designed, whether intentionally or not, to grow them (high nutrients, still water, low oxygen)
so you could keep the existing design and harvest the plants as mulch or animal feed
or change one or more of the design parameters
which ones would depend on you intended use of the pond
herbicides will kill the plants but will not change the design, so they will eventually return.
herbicide will also contiminate the pond, reducing its ability for irrigation or animal watering

check to see where the nutrients are coming from, runoff from fields, septic drainage, etc to reduce nutrient input
by changing design, ie, lower nutrients, more aeration, moving water, you will select for a different set of dominate plants in the pond. duckweed and watermeal will still be there around the edges but not "pests" anymore

Duane,

Thanks, some good ideas there.

I agree with you that watermeal and duckweed aren't evil (and are ontologically good, just maybe not good in certain situations).

As far as what I hope for the pond -- can I choose all of those options? : ) Seriously, I'd love to stack the functions. Right now I don't have the capability or need to use it for irrigation but perhaps someday. Swimming would be great. Fishing would be awesome.

As far as looking pretty. . . well yes. But, to me, the aesthetics are evaluated from the perspective of use. If I am using the pond to harvest duckweed and watermeal than a totally covered pond would be aesthetically pleasing to me.

I'd like to explore that a bit: how do people go about harvesting watermeal? And what can you do with it? I can imagine it as a compost/mulch ingredient. . . but it is awfully hard to scoop up. These things are TINY. And how to feed it to animals, and which animals?

My current thinking mirrors yours: if I want to get the pond clear I'll need to change the design. I'm working on thinking that through, and identifying the nutrient sources that might be causing this watermeal situation.

Personally I would manually harvest as much of the watermeal as possible before introducing the koi. 

judging by your zone you must not have the asian waetrmeal, which is supposed to be a pretty good foodsource. as much protein as soy beans, and used in soups, baking, etc., in asia.


Id also wager that if your hitting -15f in the winter the bottom of that 9' pond isnt freezing. Id throw in some tillapia just to see how they dop. next spring. cant hurt, keep them ion a floating cage if you want to insure harvest. if the top of the cage goes free of the watermeal, you may be onto something. let a few out of various sizes to see if any make it. maybe big ones last die to fat through low temps, maybe small live due to smaller/lower food source intake needs.

id be curious to know who lives there now- what the species of trees are around the pond and what fish/birds and other water plants are at the pond.  pictures perhaps? I suspect your design tweak will be in changing nutrient loading or harvesting for mulch/food/fodder. most northern fish sp. are at least omnivoruous if not simply carnivorous- many are even cannibals. however, some sunfish (bluegills esp) will eat plants when other food sources are low. but youd be remiss to introduce them if you had any happy intrinsic local insects or fish cause they would be eaten first. the bluegill specialize in eating other fishes eggs... but after that they go for plants... anyhow, trees and other plant, insect and fish species of note could clarify some directions.

as for harvesting watermeal i would get out there on a dingy and dip a porch door insect screen in the water, scooping it out. just to get a 5g sample and see what can be done, dry it, eat some, use as mulch, see if animals eat it when dried as a feed ammendment...when you know what to do with it focus on methods of larger harvest. having a big pile of  new chores without a certain product can get sorta overwhelming. well, I get overwhelmed. Im so buried in half starts its redonkculous

Tilapia die at water temperature 50F.    They might be pretty darn unhappy in a northern pond.

I got rid of duckweed in my small pond by visiting it every day with a sifter and scooping the duckweed out until I got every piece.  It's been 2 years and it has not come back.

I thought this would be an impossible task but it wasn't really that hard.  You'll definitely want to do it when the wind has pushed it to the edge of the pond.

I think a sifter is easier than a net because you can just whack the sifter on the ground to get the duckweed out.  But you'll probably want a mighty big sifter.  Some kind of swimming pool tool would be good.

Is it possible to drain the pond?  e.g. via siphon.  Land managers around here do that to control non-native bullfrogs.  Although I know nothing about watermeal so it may come right back when the pond is filled?

adunca,

Good ideas, however, the difficulty is the size of the pond -- a 1/2 acre is alot of watermeal floating on the surface. And to drain it would mean alot of water has to be put somewhere else (.5 acre X 6ft depth average). Watermeal is prolific, from what I understand. If you miss a bit it will come back. And they hide in the muck on the bottom, so draining would need to be accompanied with a drying out process and/or a dredging out process. It might not be feasible.

Joseph wrote:
adunca,

Good ideas, however, the difficulty is the size of the pond -- a 1/2 acre is alot of watermeal floating on the surface. And to drain it would mean alot of water has to be put somewhere else (.5 acre X 6ft depth average). Watermeal is prolific, from what I understand. If you miss a bit it will come back. And they hide in the muck on the bottom, so draining would need to be accompanied with a drying out process and/or a dredging out process. It might not be feasible.

Yes, I meant to say that you should try it on a small scale first.  Duckweed is also prolific, but I was able to get rid of mine.

It is also very light, so I doubt even 1/2 acre weighs much.  When my duckweed dried it pretty much vaporized.

I suspect that a combination of attacks would be best:

1. Address the excess nutrient issue which is causing it to thrive
2. Can you at least lower the water to reduce the size of the pond that must be cleared?
3. Perhaps you can plant some water plants that consume the same nutrients?

adunca wrote:

3. Perhaps you can plant some water plants that consume the same nutrients?

Good idea!  What about planting some Duck Potato (Sagittaria latifolia) and/or cattails?

there's an "app" for that

http://www.proskim.com/how_it_works.html

H Ludi Tyler wrote:
Tilapia die at water temperature 50F.     They might be pretty darn unhappy in a northern pond.

yes, thats the case. they do die in cold water. so the attempt at bilogical control has a clear and unavoidable control. most ecologists would be thrilled at the prospect of using species which cannot become invase to control a noxious or invasive species. saves a lot of downstream heartache over unintended consequences.  If the Tilapia prove effective at some control of the issue, its a piece of understanding the whole flow of energy and nutrients. thats also a good reason for caging them- its still clear if they are eating the watermeal and it is a measure of assurity that they dont get out, eat other stuff that might be usefull ore wanted in the pond, and they can also be harvested. and thats whiy id start looking at regional local analogies- like the bluegill, which isnt quite up to snuff I'd imagine, but theres loads of trails to follow from there. which is the whole point of my ramble, really.

personally, I wouldnt do tilapia. Id find a very local solution. including exploration of intent to grow the stuff for harvest for other reasons. In the process of design brainstorming- which isnt the process of building and managing- I dont disclude anything. So but your notion about them dying and being unhappy- well, if the notion of any fish introductions at all hasnt evolved- through research and then some trial and refinements,  into something usefull, local and with clear reasonable controls, including  those which prevent fish misfortunes, Ill throw the option out.

that question of nutrients around and loaded into pond, the major tree species surrounding it will tell alot of that story. conifer? deciduous? mature forest? young? nutrient cycling in these are all very different. while the water is likely at least mildly acidic, what maintains that is very different between conifer and deciduous and even among deciduous sp. the acididty arises in some fascinatingly diverese ways. one other thing is pretty likely- the available oxygen in the pond is being used up  if its still water covered with green stuff.  interesting set of brain candies here for a fellow like me. thanks for sharing, love to hear about those surrounding trees.

Deston,

This is all great stuff, keep it coming folks!

I will get busy on id'ing the trees. For now, I can say that they all are deciduous. I see what looks like alot of acacia or psuedo-acacia. There are one or two mulberries.

Load of turtles, supposedly called "paints". I haven't seen any snapping turtles. There were 3 muskrats living in it last fall. Haven't seen them so far.

The trees are all right on the water line, so they drop their leaves in the water. Who knows for how long this has been going on or how deep the muck at the bottom is!

right off the bat, with those two species, you have soil that is less acidic than Id have wagered. very interesting. mulberry tolerates, even likes alkaline soils. how hot do you get in summer? the USDA scale is worthless as far as im concerned. the freeze out is one of about 20 metrics that are easy to consider in climate zone ID. I bet you get pretty warm. 90 fequent with 100f waves? mullberry and acacia like heat. with turtles you ve got amphibean food in there, and small fish too. loads of water insects. thats when I start really looking at if introducing a bluegill is a good idea- cause if you have fish, youre likely to loose them with any of the regular northern omnivores, except the ones you already have. the leaf drop on water will acidify the water but if soil is alkaline and water has complex (hey, muskrats are pretty hgh up the food chian) ecology, its all fine. Id be surprised if you have any weird chemistry happening. just a little lessa acid than Id have thought. complexity's got a set of limits (some more and some less desirable) than a acidic pothole filled with watermeal.

stocking tilapia in mid spring will lead to harvest in late fall- probably aorund the first long sting of air temp below 40f, when water temps start to drop in late correlation. depends on how much light and insulation the pond get- loads of insulation, not much light I would estimate by the description.... Recommended stocking (15 to 20#) of  tilapia (Oreochromis mossambicus) per surface sf for a 8 ft depth- a cage of 10x10 at 4 feet deep woudl call for about 700 fry. but if you have bass or crappie, that cage should be 1" mesh and the tilapia to big to get out and a 1' rim up over water- see how quick this gets convoluted? thats why I brainstorm alot. ill talk myself out of this. and n the p[rocess come up with something alot lazier. like letting you do the work? maybe Ill sleep on it and see if I get any clear notions. this is one of those design problems that take some time to observe the integration of  issues, clearly!

Deston,

I am enjoying your brainstorming and am as intrigued as you are. Tell you what, let me take some pictures for you!

-Joseph

If the water temperature is too low, the Tilapia aren't going to eat much watermeal.    They'll just sit there being miserable.

"The intolerance of tilapia to low temperatures is a serious constraint for commercial culture in temperate regions. The lower lethal temperature for most species is 50 to 52o F for a few days, but the Blue tilapia tolerates temperatures to about 48o F.

Tilapia generally stop feeding when water temperature falls below 63o F. Disease-induced mortality after handling seriously constrains sampling, harvest and transport below 65o F. Reproduction is best at water temperatures higher than 80o F and does not occur below 68o F. In subtropical regions with a cool season, the number of fry produced will decrease when daily water temperature averages less than 75o F. After 16- to 20- day spawning cycles with 1/2-pound Nile tilapia, fry recovery was about 600 fry per female brooder at a water temperature of 82o F, but only 250 fry per female at 75o F. Optimal water temperature for tilapia growth is about 85 to 88o F. Growth at this optimal temperature is typically three times greater than at 72o F."

http://www.thefishsite.com/articles/58/tilapia-life-history-and-biology