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]

Wow, David, I'd call that a mighty successful food growing operation. Do you feed your tilapia anything else? I've discovered that mine love the algae from our decorative ponds, by the way. Great to stop cursing that stuff as I throw it on the compost pile.

OK, I'm going to add in some fish emulsion, and ask my buddy Nate if he can bring me some of his favorite varieties when he comes through town to deliver our first load of towers(exciting!!!). Nate, do you have Texas sized duckweed (would that be Donald Duckweed?) like David uses? I've also heard there is a gorgeous red variety....

Thanks everyone for your help! I'll let you know what happens

[Greener]

After some debating I decided I wouldn't grow duckweed for fish food (in addition to worms), instead I would grow fast-growing high-protein green plants that the fish would like to eat. I hear some love watercress, for example. In the end I decided it would be easier to grow that than maintain duckweed, though I have no idea yet if I will be able to grow enough greens for the fish! I assume the main advantage to duckweed is how fast it doubles in size/weight?

[David Hart]

Yes, I feed commercial pellets, besides the duck weed.

Sylvia Bernstein said:

Wow, David, I'd call that a mighty successful food growing operation. Do you feed your tilapia anything else? I've discovered that mine love the algae from our decorative ponds, by the way. Great to stop cursing that stuff as I throw it on the compost pile.

OK, I'm going to add in some fish emulsion, and ask my buddy Nate if he can bring me some of his favorite varieties when he comes through town to deliver our first load of towers(exciting!!!). Nate, do you have Texas sized duckweed (would that be Donald Duckweed?) like David uses? I've also heard there is a gorgeous red variety....

Thanks everyone for your help! I'll let you know what happens

[TCLynx]

It is important to note that if you want to harvest anything from a system, you are going to need some input. If you expect to get the fish to grow fast, you will need to feed pellets along with supplemental feed and if you expect enough excess nutrients to also grow veggies as well as fish feed, you will be needing to add something to produce those nutrients.

You don't get to have an aquaponics system that only produces fish, veggies and fish feed all for harvest. Something must go in in order for there to be much to harvest. The sun and air can only add so much, at some point you must feed the fish or add something to feed the plants in order to expect the system to feed you.

[Sylvia Bernstein]

Travis Hughey is a big fan of water lettuce, BTW. He says it grows faster than duckweed and he feeds it to the fish and his chickens. A thought...

Greener said:

After some debating I decided I wouldn't grow duckweed for fish food (in addition to worms), instead I would grow fast-growing high-protein green plants that the fish would like to eat. I hear some love watercress, for example. In the end I decided it would be easier to grow that than maintain duckweed, though I have no idea yet if I will be able to grow enough greens for the fish! I assume the main advantage to duckweed is how fast it doubles in size/weight?

[TCLynx]

I found that water hyacinth seem to be a favorite food of my ducks and chickens. Too bad it is illegal to have it here (of course if I ever get any it won't last long once the birds discover it.)

[Sylvia Bernstein]

True, true. I have yet to hear of anyone who has a successful system running on duckweed, worms, BSF, etc alone - has anyone? The addition of a high quality feed seems to insure that your plants are actually getting all the micros they need as well as the fish. I think of it as a vitamin tablet that insures that no matter what your fish eat they are still getting a balanced diet.

TCLynx said:

It is important to note that if you want to harvest anything from a system, you are going to need some input. If you expect to get the fish to grow fast, you will need to feed pellets along with supplemental feed and if you expect enough excess nutrients to also grow veggies as well as fish feed, you will be needing to add something to produce those nutrients.

You don't get to have an aquaponics system that only produces fish, veggies and fish feed all for harvest. Something must go in in order for there to be much to harvest. The sun and air can only add so much, at some point you must feed the fish or add something to feed the plants in order to expect the system to feed you.

[Greener]

Aha I just saw your question Silvia. Just asked the same in the 'Fish Food' discussion.

Good point about getting the full range of necessary nutrients into the system.. but could a combo of home-grown feeds provide a balanced input?

Unfortunately water hyacinth is illegal here too.. bummer. I was really excited about it. I will look into water lettuce, thanks.

[M Cosmo]

You need to check in with mark in fl.  He has some great duck weed going. 

[TCLynx]

Sounds like David Hart has some good stuff going too.

Michael Cosmo said:

You need to check in with mark in fl.  He has some great duck weed going. 

[mark clark]

duckweed seems to do best with a steady trickle of fish water, in full sun the water will get hot if it is not exchanged
right now i have 2 half 55 gal growing
i feed about 1/4 of area to fish daily, just a treat, along with algae and of course PELLETS
i have two types, one seems to do better at different times of year
tilapia will out eat it once they get big enough, so you have to keep fry out of the tank
mark

[Mark Ellis]

Hi Sylvia,

As silly as this sounds, do you actually have duckweed ro some other species like azolla?

I also cannot believe that in a nutrient rich water that it isnt going gangbusters. Do you have some close up pics you could post?

Cheers
MarkEinOz