Duckweed problems

[Sylvia Bernstein]

OK...I sadly admit that I"m about to give up unless someone here can show me the way to get this stuff to grow!.  I've had two black bins, each about 6 - 8" deep with water (I let it fluctuate quite a bit) that I put duckweed in in late June and it hasn't done a damn thing.  It is relatively shaded, gets no extra oxygen, and has had several doses of fish water, alternated with dechlorinated hose water.  I"m starting to grow some lovely algae but no duckweed....can't believe I can't grow a weed!  Any thoughts?

[Sylvia Bernstein]

Been meaning to do that, Mark. I'm leaving on an early flight to Chicago tomorrow morning, but I'll post when I return at the end of the week.

[Lori Platt]

Sylvia, I have duckweed in a plastic bin, sitting under an olive tree...has one goldfish in it (I guess he provides just enough amonia)...the duckweed grows fine:-) My problem is that my tilapia seem to think the stuff is yucky and don't eat it! I've put some in a few times (into the main fish tank) and it seems to just float around, eventually get caught in the pump filter, and not provide the least nutrition nor entertainment to the fish! Maybe it is a more *adult* taste? My tilapia are young - 2 months old... might that be the issue??

[Sylvia Bernstein]

Interesting idea, Lori. Never occurred to me to just put an ammonia generator in there. thanks for that!

Lori Platt said:

Sylvia, I have duckweed in a plastic bin, sitting under an olive tree...has one goldfish in it (I guess he provides just enough amonia)...the duckweed grows fine:-) My problem is that my tilapia seem to think the stuff is yucky and don't eat it! I've put some in a few times (into the main fish tank) and it seems to just float around, eventually get caught in the pump filter, and not provide the least nutrition nor entertainment to the fish! Maybe it is a more *adult* taste? My tilapia are young - 2 months old... might that be the issue??

[Ingo Bläser]

I´ve got Duckweed in my pond. In the main pond its eaten by fish but in the runnel and the reservoir (where is no fish) its growning like crazy unless there is very much flow (it gathers at obstacles like old wood). The water is very clear, without much ammonium and nitrite/nitrate. But what I noticed was, that it grows in areas, where there is not much light. Its beneath the plants like lilys, bullrush and other plants which take away most of the light.

[Joel G]

Hi, Lori!

Young tilapia often prefer meat/other fishes. They would even eat smaller tilapia (which is why the recommended way to grow large number of fry/fingerlings here in the PH is to segregate them into up to 10 different sizes. When they are older (breeder size), they would often let the fry survive instead of eating them outright.

 

My tilapia fry/fingerlings start to eat duckweed when they are about one (1) inch long.

 

Lori Platt said:

Sylvia, I have duckweed in a plastic bin, sitting under an olive tree...has one goldfish in it (I guess he provides just enough amonia)...the duckweed grows fine:-) My problem is that my tilapia seem to think the stuff is yucky and don't eat it! I've put some in a few times (into the main fish tank) and it seems to just float around, eventually get caught in the pump filter, and not provide the least nutrition nor entertainment to the fish! Maybe it is a more *adult* taste? My tilapia are young - 2 months old... might that be the issue??

[J Shocklie]

ha!

Sylvia Bernstein said:

So could the solution really be as easy as suggesting my hubby have a pee party? He hasn't been able to do that since the last AP system we cycled...he would be thrilled!

[Earl Phillips]

Sylvia:   I have been going thru a similar thing with some I bought about a month ago to grow for my Tilapia. I had  read some material on growing the stuff and I decided that it was not getting enough lite because it was shaded from the sun by 1/2 of my grow bed above. A friend gave me two two bulb 4' fixtures and I installed them and run them 24/7 (florescent fixtures) on the duckweed. It is letting me feed a hand size net with a 1/4" covering to them 2 or 3 times a week and I seem to be holding my own in 12sf IBC container .Is that what you found or was your growing area indoors or out and what did you do to solve the problem?  .I am sure you solved it and I hope you are doing better than I am. Earl Phillips  

[Jim Troyer]

I have Water Hyacinth and the Tilapia don't care for it.  Also WH seems to stunt the growth of duckweed. 

My duckweed is grown in the fish tank.  I have 2 pool noodles joined to make a ring that floats on the fish tank.  It is covered with fine net cloth from the fabric dept. and the duck weed grows in the net over the tilapia.  The duckweed will never feed them but I figure it helps balance out the plant load over time and it's a nice treat for the fish.

BTW:  expecting to get more a system than you put in is never gonna happen.  We know this because "the law of conservation of energy states that the total energy of an isolated system cannot change—it is said to be conserved over time. Energy cannot be created or destroyed, but can change form"

[TCLynx]

Water Hyacinth and duckweed will both use ammonia directly and can both be very heavy feeders.  The Hyacinth likes more sun and heat, the duckweed needs more dappled shade or cover.  I know duckweed likes relatively still water but it will grow best with very good dissolved oxygen or aeration provided it has a relatively still area to grow at the same time.

The water hyacinth is illegal where I am but my ducks and chickens will quickly eat all evidence of it should I ever get my hands on any.

By the way, my ducks are nuts over duckweed.  I think duckweed is even better to feed to the ducks than to try to make my fish eat it.  I can set up a kiddie pool with a fence around it so that the ducks can only stick their head through to the edge of the pool.  They will manage to slurp water through their bills until they suck all the duckweed from the surface of the pool even if they can only just stick their bill in the very side of the pool.  Seems to me a rather impressive feet.  The tilapia had to be left without food for days before they would eat duckweed but the ducks will choose duckweed over many other types of good food that they normally eat happily.

Just a general note about duckweed (or anything else that is called a weed.)  A weed is only a weed if it is a plant that is growing where you don't want it.  If you are trying to grow it, you may find that it no longer grows like a weed anymore.  Is this just a matter of perception?  Or some strange quirk in the law of plant behavior?  Those people who hate duckweed spend all sorts of effort to eradicate it from their systems and never quite succeed and the people who want to grow it rarely find it as easy as they thought it would be.  I would recommend making note of where it seems to grow best (but don't look it directly in the eyes because it might catch on) then set up a replication of those conditions as closely as possible but be sure those growing areas can also be used for other purposes as well so you can pretend you set it up to say "grow water chestnuts" or something else instead.  Then when you never get around to planting out the "other stuff" and you have to keep cleaning off a portion of the duckweed on a regular basis, you can pretend it is a chore and be sure to grumble about it so the duckweed can continue thinking it is a weed and keep growing like one.

[Jack Rife]

I HAVE A CHOP SYSTEM AND USE THE SUMP TANK TO RAISE MORE DUCK WEED THAN I NEED FOR 30 FISH. I FREEZE THE OVERAGE IN ICE TRAYS FOR WINTER USE. DROP THE FISH TANK AND RAFT BED DRAIN LINES INTO A BUCKET WITH HOLES AROUND THE BOTTOM,  THIS STOPS MOVEMENT OF THE WATER. DUCK WEED LIKES QUIET WATER.