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Roger L.
07-09-2013, 01:35 PM
I have collected some duckweed and have a second container to grow it in. My question is how to give it to the fish? Do I dry it and feed it as flake? Or, do I just pull some out of the container and place it in the tank? If fed fresh, why not grow it in the FT and just cull out any excess?

davidstcldfl
07-09-2013, 02:07 PM
When I used to grow alot...I'd spread it thin, on some old window screens, set up in the shade. The fish weren't that crazy about it dried...they perfered fresh.
I stopped drying it, but since I'm in FL...I usually have live plants to feed them most of the year.

If you try growing it in the same tank with the fish...they most likely will eat it as fast or faster then it can reproduce. At least my tilapia (pigs) did. My gold fish would eat it too.

I raised it in a seperate container ( a kiddie pool). I noticed dead leaves built up pretty fast in the bottom. If I recall, the plant has a short life span, so the dead stuff tends to build fast.

I'd just toss a bunch into the fish tank and they'd clean it up.
If your fish don't seem to eat it at first....stop feeding them for a few days. They'll figure it out. The adult tilapia seemed to like it more then the younger ones.

Roger L.
07-09-2013, 04:02 PM
Thanks David. We'll see how they like it once it starts multiplying for me.

eddiemigue
07-10-2013, 09:39 AM
I have a separate thank with duckweed and have feed it fresh to the tilapia in small amounts. Gone instantly. Once it multiplies enough, I'll supplement my feed with it regularly.

JCO
07-15-2013, 11:53 PM
Roger_L where did you get your duckweed from? :mrgreen:

Roger L.
07-16-2013, 07:39 AM
Small lake in the city park at the end of my street. It does not seem to be growing as we'll as I had hoped. Not sure why?

keith_r
07-16-2013, 08:11 AM
duckweed prefers still water, i grew it in full sun or partial, it takes over my 55 gallon tanks using just flourescent lights(that i use for crayfish) - i scoop out duckweed by the net full, and put it in the pool with the tilapia..

urbanfarmer
07-16-2013, 10:25 AM
Are you sure it's duckweed?

I just throw mine to the fish fresh. They gobble it up quickly unless they just ate.

bsfman
07-16-2013, 11:22 AM
I grow mine in a large kiddie pool in full sun. I scoop out about 1/3 with a net every 3 days or so. At that feeding rate, it replenishes itself as fast as I feed it. (I fertilize it with humonia several times a week.) I'm guessing I feed 6 to 10 pounds of duckweed to my tilapia weekly. An added benefit is that the tree frogs love to lay eggs in the kiddie pool and the tilapia will DEMOLISH a netfull of pollywogs!

I've lost a large percentage of the duckweed crop this week due to heavy rains and my failing to drain the surplus water from the kiddie pool. Overflow washed away most of the crop, but it'll rapidly replenish.

Roger L.
07-16-2013, 01:07 PM
Urban farmer, I'm pretty sure it is duckweed as compared to all the pictures and descriptions I can find. I have moved my grow container where it will receive direct morning sunlight and will get another fresh batch of the duckweed to see if I can get it to grow.

eddiemigue
07-16-2013, 05:21 PM
A question for the duckweed experts - I setup a dedicated duckweed tank with a small amount of duckweed that I had quarantined for some time. The plants seem to multiply and spread to the whole tank, which is integrated into the AP system, but they later contract, never getting to densely cover the tank. I have not been harvesting the plants, waiting until the tank is saturated, but this is going slowly, and a portion of the plants seem to be dying (turning grey).

The tank has four 100W equivalent CFL's over it, temp is 80-90F in the room, water temp is ~85F, and humidity is ~70%. So what is keeping the duckweed from flourishing?

Roger,

Don't mean to hijack your thread, but figure that this is inline with the topic and the answers may be helpful to more than just myself.

Roger L.
07-16-2013, 06:32 PM
No hijack taken Eddie. I am having problems and am looking for that one bit of info I have missed and then away I go. I hope! Everyone says how easy it is to grow so I got to thinking my thumb must be made of concrete.

urbanfarmer
07-16-2013, 07:27 PM
A question for the duckweed experts - I setup a dedicated duckweed tank with a small amount of duckweed that I had quarantined for some time. The plants seem to multiply and spread to the whole tank, which is integrated into the AP system, but they later contract, never getting to densely cover the tank. I have not been harvesting the plants, waiting until the tank is saturated, but this is going slowly, and a portion of the plants seem to be dying (turning grey).

The tank has four 100W equivalent CFL's over it, temp is 80-90F in the room, water temp is ~85F, and humidity is ~70%. So what is keeping the duckweed from flourishing?

Roger,

Don't mean to hijack your thread, but figure that this is inline with the topic and the answers may be helpful to more than just myself.
Define slowly.

keith_r
07-17-2013, 05:50 AM
i've found that once it spreads, you have to start harvesting, if it overcrowds itself it will start to die off..
duckweed grows cyclically,, there's some pretty interesting reading on the net, but the gist of it is that duckweed doesn't flower, it reproduces asexually.. the "daughter" plants have shorter, and shorter roots as it reproduces, until the roots are too small, when many of the plants will "die off"..then the cycle starts with the remaining surviving plants that manage to grow some roots..
i think it's a good idea to have a multiple cultures of duckweed...i have it in all my glass tanks, with different light durations, and will take a handful from one to the other tank to keep mixing up the "gene pool" of the duckweed, since i started doing this i haven't had a single "die off"

eddiemigue
07-18-2013, 01:11 PM
My duckweed tank has been setup for about a month, and in this time vegetation looks sparse, and is not multiplying as I would have expected. I thought that this would double every few days, and it seems to be growing at a snail's pace.

Roger L.
07-18-2013, 01:15 PM
Eddie, that is the same thing I have noticed. It does fine in the pond I got it from and I even brought some of the pond water back this time to experiment with in another vessel outside. I would check on it but there is thunder and lightning out right now, no time to be outside.

keith_r
07-18-2013, 01:41 PM
what are you "feeding" to your duckweed tank?

Roger L.
07-18-2013, 03:49 PM
I cycle the water in the fish tank to the duckweed and have even put in some Maxicrop to help it along.

urbanfarmer
07-18-2013, 09:41 PM
I cycle the water in the fish tank to the duckweed and have even put in some Maxicrop to help it along.
That's got a ton of salt in it. What's it say on the bottle? 1% Na??? And salt doesn't evaporate; it just builds up in the system!

Salinity (Salt) Stress. Another stress factor is salinity, the concentration of sodium chloride in the water or soil. Worldwide, salinity is a major factor in what plants can grow where. Salinity can be high because of the presence of sea water, as in tidal marshes and estuaries, or because of leaching from saline soils at inland locations. Duckweeds, like many plants can tolerate a small amount of salt. Small amounts are even stimulatory for growth (figure). However, above a threshold (>60 mM NaCl), growth is begins to be inhibited. At yet higher concentrations, duckweeds cannot survive.

http://www.mobot.org/jwcross/duckweed/Lemna_growth/nacl.gif
Figure: Growth of Lemna minor in diluted sewage with added amounts of salt. Error bars are +/- standard error.
Growth conditions starting with three replicates of 10 plants/each were: seven days at 20 C, 2700 lux from CW fluorescent lamps, in 100 mL 2% swine waste in 125 mL bottles with loose-fitting clear plastic lids. Regraphed from Stanley, RA and Madewell, CE (1976) "Chemical tolerance of Lemna minor L." Tenn. Valley Authority, Muscle Shoals, Al. Circular Z-72, 17 pp. (Polycopy).

Just FYI, >60 mM NaCl is about >3 ppt NaCl.

urbanfarmer
07-18-2013, 09:57 PM
A question for the duckweed experts - I setup a dedicated duckweed tank with a small amount of duckweed that I had quarantined for some time. The plants seem to multiply and spread to the whole tank, which is integrated into the AP system, but they later contract, never getting to densely cover the tank. I have not been harvesting the plants, waiting until the tank is saturated, but this is going slowly, and a portion of the plants seem to be dying (turning grey).

The tank has four 100W equivalent CFL's over it, temp is 80-90F in the room, water temp is ~85F, and humidity is ~70%. So what is keeping the duckweed from flourishing?

Roger,

Don't mean to hijack your thread, but figure that this is inline with the topic and the answers may be helpful to more than just myself.
If I had to take a wild guess, I'd say it's not getting enough light. It could be something to do with the water quality as well. The grey is probably mold eating your duckweed. Take a good picture. Maybe someone can spot something.

keith_r
07-19-2013, 05:12 AM
if your ft water is flowing through the duckweed tank, you may have too much flow..
i ended up taking one of those small plastic yard ponds, and setting it next to my main system, i used the ft water to fill it and put the duckweed in it.. at first i had an airstone in the duckweed tank, as well as a couple minnows and a single crayfish..i also put the wife's pond lilly in it....after about a week i thought it wasn't really doing much, so i removed the airstone and put it back in the ft.. thats when the duckweed growth really took off..
it was in the shade most of the day, and got maybe 3 hours of direct light..
so my experience showed me that it really prefers "still" water.. i have compromised and put air in my tanks (via sponge filters) because of the livestock, but try to tune them fairly low..

bsfman
07-19-2013, 06:51 AM
if your ft water is flowing through the duckweed tank, you may have too much flow..
i ended up taking one of those small plastic yard ponds, and setting it next to my main system, i used the ft water to fill it and put the duckweed in it

I agree, Keith. My duckweed wading pool was originally filled with FT water, but now just gets replenished with rain water. A couple times a week, I dose it with urine. It also gets fertilized with leaves that blow in and the occasional over-ripe papaya that falls into it from the tree above. I use no aeration or circulation or other fertilizer whatsoever. I may have said before, I harvest about 1/3 of the duckweed twice a week and it stays replenished at that usage level. My duckweed pond is in full sun until about 3pm. I've seen reports that duckweed can double in 24 hours, but that may be way too optimistic for practical application. Based on my own system, doubling takes about 9 days.

Roger L.
07-19-2013, 07:13 AM
I may have not been clear, I do not have my small containers in the system. One container is inside of my basement window and the other is outside of the basement window. The one outside is the one i am using the pond water in. i hope that takes off and i can harvest that to supplement the one inside as right now both are rather small trial setups. I just use fish tank water to replenish the one inside. Bsfman, do the duckweed need a high ammonia level? Or is that just a convenient place for relief?

keith_r
07-19-2013, 07:27 AM
duckweed does take up ammonia directly, i used the aged humonia i had from my cycling and dosed the dw tank with that - urine takes a few days before ammonia shows up

urbanfarmer
07-19-2013, 10:14 AM
I may have not been clear, I do not have my small containers in the system. One container is inside of my basement window and the other is outside of the basement window. The one outside is the one i am using the pond water in. i hope that takes off and i can harvest that to supplement the one inside as right now both are rather small trial setups. I just use fish tank water to replenish the one inside. Bsfman, do the duckweed need a high ammonia level? Or is that just a convenient place for relief?
Like most plants, duckweed readily uptake ammonia. Ammonia only takes 5 ATP to remove the nitrogen for nutrition whereas NO2 takes 15 ATP, this is 300% more energy. So, it's less work for the plant to take up ammonia; however, too much (because the radical free ions in the plant intra/extracellular areas cause damage) becomes toxic. FOR DUCKWEED, studies show a concentration in the water with an upper limit of about 60 ppm; however, optimal growth occurs around 10-15 ppm of N in the water. Light, temperature, and pH affect the the metabolism of the duckweed and the biochemistry of the water, but if you play with it long enough you will get a handle for what does best based on your setup.

Let's not forget the other elements essential for plant growth. Phosphorus is important to control too. :mrgreen:

JCO
07-19-2013, 02:15 PM
I gather and feed 3 to 5 pounds of fresh duckweed to my 60 1-1/2 yr old Japanese Koi every other day. I have been doing this now for the past 3 months as I do every year once the weather warms up enough for it to start reproducing at a rapid rate.

They devour it like candy. Even if it were not doing them any good nutritionally or not, which I believe it is, I would do it for the shear joy of watching them devour it. 8-)

I can't see why anyone would ever want to dry it before feeding....fresh is always better...feeding live brine shrimp is far better than freeze dried or any other way and the same with duckweed. :mrgreen:

Roger L.
07-19-2013, 10:16 PM
As I keep watching the fish I have found they act like children. Give them the good stuff and they ignore the veggies. My routine was to collect water samples to test and then as I finished the test and waited for my 5 minutes to evaluate I would feed the fish and then treat the water after assessing the test results. Then I read about this duckweed stuff and thought I should try to do this, so after feeding my normal feed I added some duckweed. They all came up to look but no one was really interested. I was having trouble with the growth part so I didn't have much and each time I fed I got the same response. I am still working on getting that silly plant to propagate as fast as they say it does so I can expand in production size (try small-loose small). The other day while going round 2 with the duckweed, I changed my routine. I took my water samples but before beginning the test portion I put a forkful of duckweed in the tank. Well what do you know, they will eat their veggies if served before the main course. Every time I've done this they are eating more and more. I did notice though they tend to eat all the roots and leave some of the leaves. This raised a couple of questions for you, my learned teachers. Is it a matter of size that they are not devouring the leaves? If they are only eating the roots, can I return the leaf to the duckweed tank to re-root (like the potato piece on toothpicks over the jar of water experiment in 5th grade)? Currently I remove any leftovers before I do anything the next day and just toss it.

bsfman
07-19-2013, 10:42 PM
Is it a matter of size that they are not devouring the leaves?

Possibly. What kind of fish do you have and how big are they?

I wouldn't worry about straining out the unfinished duckweed after feeding though. They will get to it eventually and until they do, it won't hurt anything.

Roger L.
07-19-2013, 10:56 PM
I am growing tilapia and they are about 1 1/2" - 2 1/2" except a few runts, they seemed to like the duckweed the most as they don't have to muscle around with the big boys as much. There are 25 tilapia and 16 guppies in 175 gallon tank.

keith_r
07-20-2013, 09:16 AM
smaller fish need more protein.. my tilapia didn't show much interest in duckweed until they were over 4", but they loved the scuds, crayfish, minnows and aquamax

eddiemigue
07-20-2013, 08:44 PM
Interesting read. I had added an airstone thinking that maybe lack of O2 was part of the problem, but that's the opposite of what I should be doing! The water flows from by sump up to the duckweed tank and then overflows into the FT. The water is relatively still, but there is a high exchange rate. I'll have to setup a different, stagnant tank with some of the duckweed and see if it fares much better.

Roger L.
07-20-2013, 09:24 PM
I did the same thing too Eddie. Adding more ammonia seemed to be counter-intuitive. This is why I needed this forum, I couldn't find the book "Aquaponics" for the simple minded. Thanks for the input because for the short time I have changed things around it seems I am getting some growth in my outside container. Another week or two of testing and if it goes well we be bringing in a kiddie pool.

sylvgrb
02-12-2014, 03:23 PM
I have seen systems that use plastic containers with the bottoms cut out to grow duckweed directly in the fish tank without letting it spread/take over the tank

bsfman
02-13-2014, 06:27 AM
I have seen systems that use plastic containers with the bottoms cut out to grow duckweed directly in the fish tank without letting it spread/take over the tank

What keeps the fish from eating all the duckweed out of the bottomless containers?

JCO
02-13-2014, 11:25 AM
Good question BSFman, but with the bottom cut out, how does the container float?

JeffS
03-10-2014, 08:30 AM
I recently had to move 800 1 inch fingerlings to a larger tank so I used the IBC I was growing duckweed in. In 4 days I had no duckweed.

JCO
03-10-2014, 11:27 AM
And your question is what...small fish love duckweed and now you know it to..grow your duckweed elsewhere and feed it from there :mrgreen:

JeffS
03-10-2014, 03:25 PM
JCO, BSFman, Check out this video. https://www.youtube.com/watch?v=4ksnnwxlq1g

Apollo
03-10-2014, 04:26 PM
Thanks JeffS,

Good video... I've been wanting to do this for some time now. I'm going to build a small one for my Breeding Tank and a larger one to put in my main tank.

Now, where do you buy the duckweed to start out with? Are there more than one kind?

JeffS
03-10-2014, 08:42 PM
I bought a small amount online. Don't remember where. Just a zip lock bag full. Grew it in small containers for a while. Worked but not well. Finally I had an IBC full of fish water and no fish. Dumped it all in there and it grew well.... until I put the fish in.
Now I have to get more. Might wait til spring so I can grow it outside.

JCO
03-11-2014, 08:22 PM
I have the small leaf duckweed that Tilapia perfer. I would give it to you for free and you pay the shipping but since my wife is the one who has to bag it, box it, wrap it & take it to the post office I will have to see what she wants ($) to do that and get back to you. :mrgreen:

Apollo
04-19-2014, 10:42 PM
I'm finally building the raft for my duckweed...will hope for the best.

Roger L and anyone else, how about an update on your success with duckweed.

Thanks Apollo

Roger L.
04-20-2014, 10:48 AM
I have never gotten the duckweed to grow in my basement setup. I have had other things eating up my time so I have not been working on that. Just a priority issue.