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Has anyone found a source of feed for their tilapia that doesn't have fish meal in it?  I"m not having any luck finding anything I consider sustainable so far, and I'm too busy / lazy right now to start up a duckweed system.  Thoughts?

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If you are letting the chicken waste drop directly into a duckweed pond, how will you ensure that you won't be introducing pathogens from that pond into your fish system by feeding the fish duckweed?


Don't get me wrong, I love the idea of utilizing all manure.  I'm a huge believer in Humanure compost and I've done Pee Ponics too.


However, I think there needs to be some intermediate stage with some sort of bio-digestion, composting, or sterilization by heat of the chicken manure before you use it to grow a fresh food for the aquaponics system.


Or were you planning on cooking the duckweed to kill pathogens before feeding it to the fish?

I agree with TC. With animals other than ruminants, I would highly suggest high temp composting; some sort of bio reaction or sterilization before it makes it to the duckweed, just to be on the safe side.


We are going away from using animal waste and turning to human pee next year. I'll post something when we are done. 

Yes, I agree, I have to research a way to kill pathogens...  It's one missing link yet. 

I will be researching the different methods, but cooking certainly doesn't seem feasible at ALL.  I had read in some publications about duckweed's ability to remove some pathogens  and pollutants, but I need to do more research.


Thanks for the feedback... awesome :)


I fear the duckweed's ability to remove pathogens/pollutants/waste/nutrients just means all those things are concentrated in the duckweed its self and therefore not something you want to feed to your AP system.


However, perhaps you can set up some sort of digester to utilize the chicken waste and then use the compost from the digester to feed duckweed?

Again I support TC's suggestion. One idea might to run the collection into a living machine or even a trench in soil compost catchment system if you are that lazy, but I strongly recommend looking into high temp composting. But technically, a good cold, rinse-off/ washing at harvest would take care of most of the pathogen problems. It's just a shame to waste all that perfectly good water.


However, to play Devil's advocate with myself, I'll say that the Chinese have been doing this before the bible was written and there are over a billion of them so...I'd also like to say that this type of IBS (integrated bio system) seems to work better for ducks than chooks so if you insist on this track of thinking with raw manure, you might want to switch to ducks. BTW, do people there go for duck meat? I'm in Beijing as in Peking duck.. IT IS AWSOME! You gotta come try it!

I have several Pekin ducks... and have been mulling over the use of duckweed to clean the water in a swimming pond just for them because THEY POLLUTE THE WATER UNBELIEVABLY!  I also had considered constructing an aquaponic system with the ducks solely for ornamental type growing of plants in an aesthetically pleasing arrangement just to keep the flies and odor away!  I envisioned long narrow beds as borders to a patio, loaded with small shrubs and flowers just to consume the <what we affectionately call> "duck water".  I have tried introducing duckweed to their water play areas, but they ADORE eating it and consume it voraciously before it can even begin to get a foothold.  Clearly, the duckies appreciate it's nutritional value.  They love it.

I will keep working on my plan, and look forward to your ideas... they are great.  Right now I am researching the likelihood that fish are carriers of the same ecoli as warm-blooded animals... perhaps there is a disconnect there somewhere.  I know that the bacteria can live in freshwater, thus contaminating the flesh of the fish, but do they actually carry it in their digestive tract in the same form?

Obviously a whole new topic for me, and I need to learn more.  

Thanks for the great discussion! Fascinating.

It isn't the fish that would be the vector in this situation.  It would be any raw veggies being grown in the water contaminated by fresh warm blooded manure products.

Good point, and one that I should have been thinking of, DUH.  

Also, found a lot of very technical information about this topic earlier today, here are a couple of excerpts:


Environmental conditions and wastewater treatment performance in a full-scale duckweed pond system are presented. The treatment system consisted of three stabilization ponds in series and was fed with septage. Vacuum trucks pumped the septage from residential holding tanks and discharged it to the system daily. The inflow rates averaged 36 m3 d-1 in the cold season and 60 m3 d-1 in the warm season. Duckweed (Lemna minor) colonized the ponds in the warm months and survived during the cold season. Because of the difficult process for harvesting the duckweed biomass, the investigation of the treatment efficiency was carried out without plant harvesting. Samples were collected from the vacuum trucks and from the exit of each pond and were analysed for physicochemical and microbiological parameters over a period of 12 months. The results showed that the duckweed mat suppressed algal biomass, which in turn led to anoxic and neutral pond conditions. On an annual basis, the duckweed system sufficiently removed BOD5 (94%), NH4+ (72%) and E. coli (99.65%), with lower removal of TSS (63%) and Enterococci (91.76%). A slight increase (1.1%) was recorded for o-PO43-. Between the two sampling seasons, BOD5 and TSS removal efficiencies were higher in the cold season with the longer retention time. Similar removal values in the warm and the cold season were found for nutrients and bacteria. These findings indicate that BOD5 and TSS removals are less temperature-dependent at higher retention times, while ammonia nitrogen and bacterial removals are substantially influenced by temperature as well as retention time.
And this:

As with any organic surface area enhancing material introduced into wastewater, duckweed plants do marginally concentrate pathogens on their surfaces. As such, pathogens will, inevitably, be harvested along with the duckweed crop. If harvested plants are used green as fish feed, these bacteria experience even greater dilution and faster die-off in the fish pond. The small number of surviving pathogens consumed by fish will be digested in their guts. In instances where plants are processed and dried, desiccation will achieve even more rapid die-off. No viable human pathogens could be cultured from dried sewage-grown duckweed meal in 4 years of testing. (See next footnote)

[Footnote: Haustein, A., R. Gilman, P. Skillicorn, 1987, The Safety and Efficacy of Sewage-grown Duckweed as feed for Layers, Broilers and Chicks, report to USAID Science Advisor. This research, conducted in collaboration with enteric disease experts from The Johns Hopkins University, examined both wet and dried Lemnaceae harvested from the San Juan wastewater lagoons located in Lima, Peru, for presence of various human enteric pathogens.]


And this:

The duckweed biomass that results from water treatment operations must itself be removed from the water.  This can be done by skimming it off.  Duckweed grown on sewage or animal wastes normally does not contain toxic pollutants and can be fed to fish or to livestock, or spread on farmland as a fertilizer.  If the duckweed is to be fed to animals, a retention period in clean water will be necessary to ensure that the biomass is free of water-borne pathogens.

The links on this page illustrate both potential and proven duckweed applications.

---It's a start.  


So it sounds like a retention period in clean water might work but I would say skimming and dehydrating before use as feed might be an even better way to do it.

I think I agree with you :)

Definitely a summertime project.  I am already envisioning a strong mesh screen on a frame that would work as a harvesting tool AND a dehydrating mechanism.


BENEFIT: Tilapia feed could be stockpiled!  Not such a bad plan!  


Now you've got my wheels turning :)

was thinking you could build some frames for this strong mesh screen and lay them in the water and allow the duckweed to grow over them.  then at harvest time, lift them straight up, pop them onto a few cement blocks or saw horses and allow them to dry that way.


just a thought

Sure, would get a much more even layer of duckweed on the screen that way.  When netted out and spread on a drying rack it's hard to spread wet duckweed out thin to dry.  The mesh would need to be almost as fine as window screen but would be fairly easy to do.



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