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I have been made aware of a section in the latest newsletter of an aquaponics trainer making some rather interesting statements around the risk of introducing "deadly" E. coli HO157:H7 into aquaponics systems through the introduction of worms.


Like most promotional material, it contains enough reference to some form of correct base statement to make their argument appear compelling, but I have found the way that the section was written distressing in many ways.  On one front, we are trying our level best to ensure food safety and hygene in our units and to educate people on the safety of aquaponic production methods.  To have someone from within the community write something down the line of "if you dare put worms in your system you run a very real risk of introducing a deadly pathogen into aquaponics" is not conducive to building a fair and realistic impression of aquaponic production methods.  Worms in media beds have been in use for many years outside of the design of the group in question, with no reports of any health issues.


The inference made was that (without stating how many worm growers use cattle poo) red wrigglers are likely or potentially all grown in manure from corn fed cattle and this all contains the "man made" (?????!) strain of E. coli that will then most likely survive the transfer from worm to your system where you will contaminate your crops, your family or your customers.  If you are extra unlucky, a fly from a pasture containing corn fed cattle poo will also do the trick (then why bash the worms?) if they can make the trip in under 10 seconds. 


The article would have had more use if it simply said something down the line of "pick your worm supplier carefully - if you are cautious about E. coli, steer clear of using worm growers that cannot guarantee that their worms were not fed corn-fed cow poo from feedlots." I do not know what the ratio is of worm producers that potentially use this feed method compared to those that do not, but if it is the case that very few follow this practice, this article borders on reckless.  Then one can write follow-ups warning people on the next one in a gazilion risk such as a bird-flu contaminated duck landing in your fish tank.  As stated before, in theory, the conditions described in the text can potentially occur. Just as, in theory, a monkey can sit down in front of a typewriter, hammer away at it and write something recognisable. Not impossible, but likely? 


I wrote a blog a while ago about the responsibility of perceived role models in the industry related to statements made and perceptions created from a "credible" source.  This type of statement was exactly what I was talking about.  Not worth the negativety and not worth the potential bad press and poor PR for what many aquaponic producers see as a staple - media filled beds with worms in them (is there a reason for this?).  As a scientist, I would like to see some concrete evidence related to instances of the scenario described having been observed at worm farms and in aquaponic systems.  If no such data exists, is this statement fair and accurate? Why was it made? I do not want to appear to downright rubbish their concerns, but I will appreciate a percentage risk description to back up this claim.

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Hi All,

Great discussion and very informative Kobus. If there were any grey areas concerning AP and E Coli the forum has dealt with all.these. If anything this article brought greater awareness to the need of proper hygienic practices and the potential of E Coli in AP and teaches me how to avoid/prevent harmful bacteria in AP systems, for this reason it has served good purpose. Even though AP, compared to other types of agriculture, is less susceptible to contamination, we should nevertheless exhaust every possibility possible to avoid foreseen/unforeseen dangers as will always be done on this forum!

Namaste Kobus my friend,


You know me too well by now Sir :-)


Remember many many Moons ago I posted a link for you re Worms in Media Beds by Murray Hallam...what can I say.


God bless,

Kobus Jooste said:

OK everyone - I can see where this is headed.  Statement made, follow-up published, and then the opinions of people that have read it.  If you are happy with all that were written, that is your business to be so and I'm not going to try and polarise people here.  Sahib - your desire to defuse such situations is legend and I will respect what I read between the lines here too.


That said, just a final question:  The scenario was sketched of a student buying worms from Craiglist, precipitating the need to warn all about the dangers of poo produced worms.  However ill-conceived a person may have tried to get the message across, why on earth not tell it like it is?  No mention of the student, no mention of Craiglist, no mention of the source of the worms, and no mention of the outcome of the whole event that precipitated the need for the warning.  I read it carefully as the person that drew my attention to it had a different interpretation to my response thus I was careful about reading it more than once.


Worms need to be bought somewhere.  We (almost) all put worms into media beds if we have those.  There are no records of the bacteria in question ever showing up in an AP system anywhere.  I have never seen a record of E. coli contamination in AP, traced to worms in media beds for that matter too.  What I have seen though, is a prominent member of this forum adding media beds with worms into her commercial system and terminating her training affiliation with the people that then almost instantaniously had the warning go out about worms in media beds. Funny that.  As I said before, I am not trying to polarise people, but I will be vocal when I see misinformation and I will keep an eye on how this whole episode shakes out.  I see it as a potential looming spat between two different design philosophies and if that is the case, this will not be the last of this type of event.

You guys bring up a real concern I have and need to pass by you. What about losing fish due to re-stocking and some of them dont surive and you dont find them until they are a few days dead and or nearly eaten and white in color by the other fish in the tank???? These fish are about small hand size also. This is in a Deep water trough system also???

Biggest danger with dead fish not found right away has to do with ammonia spikes and water quality problems possibly hurting your other fish.

What do your water tests say?  Stop feeding until the ammonia and nitrite are back down within the safe range.

Hi Wes, not sure where your concern lies.  Is it that their decomposition may somehow cause the introduction of a harmful pathogen into your system?  The nature of a fish's composition will not generate any such pathogens even upon decay.  The concern with that much decomposition of an organic substance, the fish, is more akin to the issues it will cause in a balanced aquaponic system, ie. decomposing matter or matter that is going aneorobic will steal oxygen and contribute to elevated ammonia levels.  This issue is irregardless of DWC or media, its just has to do with the nature of having a fish tank.  

A safe practice to help minimize the amount of decomposition you experience in your tank upon introducing some newbies is to drag the bottom of the tank daily with a net.  Dying fish tend to be at the bottom if you miss the part where they are listing and swimming sideways at the top.  You can net out the dying or newly dead ones this way before they get to the point where they are floaters.  If they are floating they have been dead for a while.  

We actually have a video on my Green Acre youtube channel about this.  I think it is called Searching for Dead Fish, real creative there, huh?  Lol.  But it is for the same exact reason as after transport fish tend to be stressed and there's a good chance some will die.  Hope that answers your question!

Wes - it all depends on how many fish is lost, their size and the volume of water in which they decompose.  As TCL pointed out - if your water tests show you have a ammonia and nitrite spike, remove what is left (dead fish) and slow your feeding until it improves.  You may also want to keep an eye on DO. In my duckweed system, Ammonia and nitrite was not an issue when a whole lot of duckweed died all at once, but I could see the issue with DO readings and had to increase aeration.  If it is a big system and a few small fingerlings, you may not even notice the loss unless you see them!



Ok, here are my thoughts on E coli and worms in a commercial system : 1. know where they are coming from  2. I would  wash them in a mild vinegar solution. Washing with water would only spread the pathogen it will not kill it. 2. I would segregate them prior to putting them into the system. In no way would I be worried about the worms them selves, just what could be on them. I should also mention before even worrying about the worms .The bigger concern with vegetables would be how they were processed and stored most food outbreaks from vegetables has not come from the farm but cross contamination from processing. But the general public would blame the vegetable itself and the growing process and not even hear where the contamination came from.

Thanks Gina and Kobus for your replys. I am in the clear with the levels, ammonia is a .50 and DO is at 10 nitrite is at

 .25 so no worrys there was just thinking of the Bacteria issue but you guys cleared that one up for me, thanks.

Sure Wes!  


Hey Earl!  Good to have you chime in!  Great points.  It is almost always at the processing facilities, in fact the most recent scare with Romaine from SoCal just a couple weeks ago is being connected to the processor.  Although I think I have to disagree just a touch that the general public isn't quite that oblivious.  I think they are slowly becoming more aware of the fact that the contamination usually occurs at a processing plant facilities.  

Well folks, it seems as if a response/clarification has been sent out subsequent to the original statements concerning E coli etc. It is pretty lengthy so I did not copy it to this forum.


Can you supply a link?


Nigel Clement said:

Well folks, it seems as if a response/clarification has been sent out subsequent to the original statements concerning E coli etc. It is pretty lengthy so I did not copy it to this forum.
Hi Nigel.  I hope you don't mind but just to keep things a bit tidier in here I'm posting the link and deleting that novel!  Thanks

Nigel Clement said:

Not sure how to link it, I'll paste it in here. If it is too long I do truly apologise.

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