Duckweed PeePonics

someguy · **Joined:** Jun 4th, '08, 10:03 **Posts:** 83 **Gender:**

sorry, i just couldn't get over the earth-is-flat link/internet-accuracy argument. i think THAT is termed minutia. but you are absolutely correct. NOBODY said accurate information could not be found on the web.

TCLynx

Ah stop bating eachother and go pee in the duckweed tank :wink:

Chappo

Yes Maam ,, and I will need some beer to ensure a good supply.

TCLynx

Would that then make it a Duckweed Pee Party :?:

I wonder if it is just the heat here lately slowing down my Duckweed. It's been 92-93 F for about the past week "droopingly hot" <need a smilie for that> I'm amazed at what plants I still have that are doing ok in this (there is still some edible lettuce in my garden) while I'm still waiting for my tomatoes to get a wiggle on before it's too hot overnight for them to set fruit.

someguy · **Joined:** Jun 4th, '08, 10:03 **Posts:** 83 **Gender:**

sure sounds like the heat is doing it.

i know i'm going to annoy the old chap again by posting a blog link here.

http://urbanaquaponics.blogspot.com/200 ... kweed.html

according to this post, it starts dying off at 92F?

Chappo

Can't really call it a party ..... I'm having a beer now alone , worked all night and the beer always tastes great.
Perhpas cold beer makes cooling pee ponic additions:)

94 .....,, AHH thats 34 C ,, HOT HOT ,, perfect beer drinking weather but yes some plants will be struggling.
The duckweed should be ok , it grows wild everywhere near my farm in tHAILAND AND IT IS OFTEN 34c THERE.
Some shading will always help.

In that heat maybe a good time to look at growing some of the tough plants from Thailand,,, Thai Basil , Royal basil etc .
Drop into your local Thai restaurant and ask what they are paying for these essential ingredients ,, you may get a pleasant surprise what price these can be sold for. OOOPS not sold , that would be commercial .....,, ahh you will be amazed what Thai food will be found in your bag after you accidentally drop a kilo of Royal Basil on the counter of your local Thai restaurant:)

DanDMan

Hey chappo, do have any idea how many square meters of pond it takes to grow enough algae to produce 1KG of dried algae?

I have tried to grow duck weed, but even when it lives I could never have enough pond to produce enough duckweed to replace my feed.

RupertofOZ

There are two types of "duckweed"...

Lemna minor L., lesser duckweed, Lemna trisulca L., star duckweed or ivy duckweed (Family: Lemnaceae)

Which is the smaller and most common variety found here in Australia and in most countries....

http://www.ecy.wa.gov/programs/wq/plant ... emmin.html

And the "giant duckweed".... Spirodela polyrrhiza (L.) Schleiden, giant-duckweed, great-duckweed, duckmeat (Family: Lemnaceae)

Which is a tropical variety.... native to Florida apparantly.... which has much higher temperature tolerances....

http://aquat1.ifas.ufl.edu/node/435

http://www.ecy.wa.gov/programs/wq/plant ... pipol.html

http://aquaplant.tamu.edu/database/floa ... ckweed.htm

I purchased both varieties.... the "giant" duckweed from the Northern Territory.... and over summer, particularly during the 40+ week we had... the "smaller" variety definitely died off... while the "giant" variety survived... although has grown much slower since the temps have cooled significantly...

I suspect the duckweed on your ponds in Thailand is the "giant" variety Chappo... :wink:

RupertofOZ

Here's a few links to studies on Duckweed...

http://www.p2pays.org/ref/09/08875.htm

http://www.fao.org/ag/AGAinfo/resources ... DW/Dw2.htm

http://www.mobot.org/jwcross/duckweed/Fish.htm

http://www.eawag.ch/organisation/abteil ... ckweed.pdf

Chappo

Yep rupe , we trialed both types of duckweed ,, the small leave one was in a smaller shaded pond that was originally built for red-claw about 3 months before Thailand BANNED the importation of Australian yabby.

I would estimate a 10% return , wet to dried.
Perhaps less.

RupertofOZ

And the Giant Duckweed??....

Chappo

We mainly harvested the giant duckweed from a local government pond ,, it was a pain in that its roots hed huge amounts of dirt/mud/silt . Sure made harvesting Moringa look easy and normal fish pellets seem REALLY cheap.

TCLynx

Well after getting some more duckweed and filling the duckweed tank with it. I found that if I don't feed the tilapia in that tank any pellets, they will eat all the duckweed in about a week.
If I fill the tank with duckweed but still feed them a hand full of pellets in the morning and again at the end of the day, the duckweed doesn't not get eaten nearly so fast.

And now that I've had tilapia breeding out of control in the duckweed tank, I've been feeding the fry some high protein starter food which is probably not only keeping the fry growing fast but also proving extra ammonia for the duckweed to thrive. I put a heavy load of duckweed into the tank a few weeks ago and there is still a good cover of duckweed over the surface.

Since I'll have to pull the tilapia out of there before it gets too cold, perhaps over winter I'll be able to grow a fair bit of duckweed to dry to supplement the next summer's tilapia feed. I just hope I can time harvesting a large batch of really tiny fry as late in the season as possible so I can overwinter them indoors. The rest of the tilapia will be getting eaten one way or another (either by the chickens, the catfish or us depending on size I guess.)

Anyway, I am really impressed about how well the fish seem to be doing in the duckweed tank. They get minimal aeration and flow yet I don't see them gasping at the surface and they do eat. I guess the large surface area has something to do with it and maybe the duckweed is helping out during the day. The Quarantine system had loads more pumping and flow yet the fish were always at the surface looking for air and were not eating well. I'll have to work on the quarantine system some more.

The Duckweed peeponics is simply a barrel ponics system with an extra tank attached to provide more surface area to grow duckweed and such. There is a far bit of gravel in the big duckweed tank. I diverted the flow from the grow beds to go into the duckweed tank and there is a standpipe at the far end of the duckweed tank that carries water back into the barrel fishtank where the pump is. If that pump is managing 100 gallons an hour at the head it has to pump for that system, I'd be impressed. There is a small two outlet air pump with one air stone in the barrel tank and one air stone in the duckweed tank. That system probably uses less than 40 watts (I don't know the wattage on that pump but it isn't high and the air pump is probably less than 4 watts.)

If some one wants to push the limits of power usage, this might be the way to do it if you have a climate warm enough for tilapia, provided they are legal in you location.

TCLynx

Well, duckweed makes a pretty good ammonia sink. While the tank was well covered with duckweed, I was able to feed quite a lot and didn't seem to be having any ammonia spikes. However, I cut the feed way down and the fish ate all the duckweed. Now I have to feed them but I'm getting ammonia and nitrite readings again.

Time to go get more duckweed. :compress:

TCLynx

Nitrates in this system are currently only a bit over 5 ppm.

pH 7.5
Ammonia .5
Nitrite trace

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