Backyard Aquaponics
A place to discuss aquaponics

i've been growing duckweed for about 4 years now.. mostly to consume nutrients in my crayfish tanks, but excess gets fed to the tilapia.. the colony does drop when it gets into the 40's, but i have not had a complete die off,
this is inside, with just flourescent lights.. i feed quite a bit to the tilapia during the warmer months

So ironic that in my fish tanks duck weed was considered a invasive plant and now I desire the growth for a sustainable fish food. It's easy easy easy to grow just get a tank or tub fill it with 5 goldfish and put duck weed in there it to thrive

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Now to get it done. On my list of things to do.


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Sleepe, that was an interesting article. Hard to believe that fish raised in sewage water were then sold as food (after a 2 week purge). I guess I won't worry about an occasional bit of Neem oil in my system anymore. lol

This was the bit that caught my interest (well and the DO levels).

"The reduction of total suspended solids (TSS) to the
extent of 53 and 37% through duckweed and fish ponds
respectively is attributable to their entrapment by the root
structure and removal along with harvested duckweed
biomass (Fig. 4; Table 1), besides accumulation at the
bottom. Van der Steen et al. (1999) reported better removal
of suspended solids in duckweed-based system due to
suppression of algal growth"

until they lose thier roots/die and become tank litter themselves.

Azolla is even worse for this.

If I understand correctly, most people grow duckweed in separate tanks, not in an FT. This makes sense to me. Shallow basins(kiddie pools is what I'm thinking) and then be able to harvest to supplement food.

I've been growing duckweed for a few years.

I'v grown it in almost stagnant water, and in high flow water with water splashing directly onto it so it gets submerged a foot deep where the water hits before rising back to the surface.



It definitely prefers not to be submerged, but still thrives here. I grew it in my topup water tank (left sitting for dechlorination) and almost killed it by adding a bit much acid (it went white), so pH might be a factor. My system runs at around pH 7.5 and I can grow half a 10L bucket full a month from the surface of a 500L round sump (water temp is currently 21c)

It also grows in a foot deep of water at the in the bottom of a wheely bin so its getting zero direct sunlight down there, but grows very slowly.

There are a few weeds that are sold locally here in plant stores as duckweed and are actually illegal to sell. They are larger of leaf, and have frilly edges and sometimes a touch of purple. So in Australia at least there's a fair chance some of the fails are due to it not actually being duckweed that people are trying.

Duckweed has a bit of a bad reputation for choking waterways because it grows so quickly, so make sure it doesn't escape to anywhere it doesn't belong.

Real duckweed looks like this...



There are a few other varieties that you can see on wikipedia

I'll empty my tank of it and do a time lapse over a month or so so you can see the growth rate. (it's getting into winter here so wont be as spectacular as it might have been a few months ago. ).


one day I'lll get around to making this...

http://120thingsin20years.blogspot.com. ... eeder.html

Got my table built. It's the top half of an IBC cage with the bottom 8" of the tote. I took the retainer bars off two other tanks and am using them as the supports for the tank. Will more than likely put a piece of 1/2" plywood between the supports and the tank to prevent bowing from weight.

Now to figure out how exactly I want it to sit over my 3rd FT. Will take pics tonight.


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Pictures as promised.



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How do you guys do your drains on your duckweed tanks (assuming they are inline/flow through)? I've found duckweed tends to clog drains quite easily but I'm probably doing it wrong

I'm interested too I'm still figuring it out.


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This might not be too helpful, but I grow duckweed in barrels and buckets, and in an old child's plastic wading pool. Since I seem to be prone to the occasional stupid self-inflicted disaster, I've recently been growing a backup supply in coffee cups and plastic "To Go" containers on my desk at work, in case I need to re-inoculate my system some point in the future.

Here's a shot of part of my "work" crop:

I try hard not to grow duckweed. It comes into our systems when we top off from the lake on the property. It gets all in the DWC rafts beds and it's like trying to get rid of roaches. I skim it out and feed it to the fish but it just comes back again and gets all on the rafts. The plants in the rafts don't like the duckweed sticking to them UGH

I can only imagine the strange looks you get around the office ;-}