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Duckweed produces no poop, no amonia

Hi,
I want to feed my fish duckweed only. Three weeks into this, the SF had no poop, the ammonia, nitrite, and nitrate are all at zero levels. Is there a relation or something else is causing the numbers to go to zero?
Any one had the same experience?

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Permalink Reply by Pieter Swanevelder on November 2, 2015 at 2:30am

Found this below - seems your duckweed is sucking all the amonia and nitrogen from your system. Where do you grow your duckweed? Maybe seperate the duckwood nursery from your aquaponics? and only feed as required?

"When grown on swine wastewater, the duckweed Landoltia punctata was shown to remove 98% of the total nitrogen and ammonia content, and 94% of the total phosphorus. Considering these are the main agents of eutrophication, or nutrient pollution, the results are groundbreaking. If that wasn’t enough, L. punctata also improved levels of dissolved oxygen, crucial for the health of aquatic ecosystems."

http://www.environment.co.za/pollution/from-waste-to-wonder-the-tal...

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Permalink Reply by Moe on November 2, 2015 at 4:56am

Wow, i have a separate setup of trays away from my aqua phonics system where I grow duckweed. Every day I use a small net to transfer some to the FT. Couple of times the water in the FT rose and some duckweed escaped the FT onto the SF and finally in the ST. I noticed them in the ST and I was happy because I thought it was an extra large "tray" to grow duckweed and it was away from the fish so they would not eat it up.
Guess what, the duckweed has been absorbing all the amonia to themselves. Amazing.
This is very very helpful. Thank you for quickly replying to me!!!

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Permalink Reply by Pieter Swanevelder on November 2, 2015 at 5:30am

thanks for the question - it triggered some memory on duckweed/AP system I've seen before and as I'm also busy with upscaling my system - considering duckweed as alternative/subliment feed. Please let us know if your system recover after removing the duckweed from ST. Some photo's appreciated to see the extend of coverage on your ST before and after.

Not sure why no visible poo though!

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Permalink Reply by Derek on March 22, 2016 at 10:02am

I found feeding my fish duckweed gets broken down much easier by the bacteria in the fish gut. So more liquid poo is often the outcome. Maybe that's why you don't notice the poo.