Aquaponics, worms and E. coli

[Kobus Jooste]

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.

[TCLynx]

Now the compost doesn't necessarily make them taste better, however good compost tends to provide necessary nutrients which can make things taste better compared to some growing method that might only be providing the bare minimum nutrients to let the plants grow (like sand and miracle grow with no compost).  It is rather beside the point of aquaponics.

 

However, it is a good point that Growing power does use worm castings mixed with coir as their potting mix for growing micro greens and shoots as well as the potted plants that are in the tops of their double level AP systems and water cress is growing in the lower levels of those aquaponics systems.  Their worms are not fed manure either though.  Their worms are bedded in wood chips mixed with produce waste and brewery waste.

 

Growing power might be a good resource for testing the safety of such things since they do use worms very heavily.  Worms are actually a bigger portion of their operation than aquaponics is and the shoots and microgreens growing in the worm casting coir mix would definitely be a good thing to test to assess the safety of worm castings for growing foods that don't get cooked.

[David Waite]

Jane I have grown alot of plants using hydro and the taste was always tinney. Unless you smoke it then it was ok hehe. I have grown tomatoes in my system this year and the taste was as good or superior to my inground vines. You will love them for sure.

Jane said:

I want to clarify a bit Growing power has tomatoes grown in pots filled with compost sitting part way down in the recirculating fish water.

[Harold Sukhbir]

Hi All,

I agree that "cured" compost is nothing more than concentrated nutrient and can be combined with AP to compensate as nutrient replacement. However if it is combined in a way that it can develop anaerobic zones we run the same risk all over again. Nutrient at best, should be totally dissolved in AP system water.

[Earl ward]

I have read the same news letter and happen to agree with the statements made. I’m not saying not to add worms to the bed, what I’m saying is what I think was the intent of the article. You have to know the source of what you’re adding to your systems.  Just like adding fish to your system, you would never want to add fish to your system without knowing the source same goes for the worms.

 

 

[TCLynx]

Yup, quarantine of worms or fish before adding into the system is a good idea.

[Rebecca B]

Susanne wrote a special newsletter:

 

"Based upon emails we've received, there seems to be some confusion in the minds of some who read our last newsletter. Here's our clarification: we are NOT saying that adding earthworms to an aquaponics system is dangerous, or even detrimental. Quite the opposite; earthworms, properly sourced, are a tremendous benefit to aquaponics Systems, and perform an essential role in systems that do not have gammarus. 

Our concern is motivated by the actions of one of our students, who recently added a media bed, and then purchased earthworms, castings, and compost combined in a gallon Ziploc bag from an ad on craigslist, and then, unthinkingly, put it directly into his aquaponics system. Earthworms can perform a useful function as mineralizers in aquaponics systems, but the compost that contained the earthworms, in this case, is of an unknown source and composition."

[Sylvia Bernstein]

I don't think that you need to quarantine worms before adding them - they aren't going to introduce a disease because they are ill themselves.  The problem is possibly what they have been living in and if you don't know what that is then you need to get if off of them.  You would have the same risk if you start seedlings using compost, right?

 

Converse had a great solution on the other thread - http://aquaponicscommunity.com/forum/topics/worms-and-e-coli?xg_sou....  I called our worm vendor, BTW, and asked what he ships in and what their process is for preparing the worms for shipment.  They essentially remove the worms from the organic compost they use, rinse them, then rinse them again, then pack them in peat moss.  He said that you would never ship worms in hot compost because it would add too much heat to the bag / box and heat is their biggest risk when shipping worms.  But, to Earl's point...know who you are buying from!  Craig's list isn't a great option...but if that is the way you go then make sure you clean them before putting them in your system.

[TCLynx]

I suppose when I say quarantine for worms I mean more along the lines of you buy worms and use them to start up your worm bin.  Then you will feed your worms safe inputs for a time so then when you are ready to use them in your AP system, they are no longer coming from an unknown/possibly dangerous source but they are coming from your own worm bin and you know what they have been fed and if there is risk of flys or other vectors associated with your worm bins.

[Earl ward]

 

I would have to say I would segregate them before adding them to the system, I would rather be safe than sorry. I would not start plants in compost either. This is for labor proposes I start in the net pots that go directly into the raft. I should also state mine is a DWC system not media. When I build the large system it will be a hybrid system incorporating both.

[Sylvia Bernstein]

Sorry if I seem like I'm nit picking this, TC, but I still disagree.  I tell my customers to buy worms from a reliable source (us) and add them straight into their systems.  This is how I do it for my own systems because I trust my worm vendor, who is not only one of the big names in vermicompost but is organically certified.  You shouldn't have to start up a vermicompost system on the side to be able to add worms to your aquaponics system...and TIME has nothing to do with it.  In fact, as I've said a few times on this thread, worms will actually take E. coli in and pathogen-free excrement comes out the other end!  The ONLY problem is what is actually on the skin of the worm...not what is inside of them.  Washing them will take care of any issue.  If you take a bunch of worms with E. coli laden compost on them, and build a worm bin with it the worms will probably eventually take care of the pathogens...but before they do the pathogens will just be multiplying in your worm bin!  It's like if you or I stuck our hand in that same manure.  It's not about feeding us a healthy diet to get rid of it....it is about washing it off our hands.

[Harold Sukhbir]

Hi All,

Precautions to safeguard against pathogens in AP

http://www.ctahr.hawaii.edu/oc/freepubs/pdf/FST-38.pdf

[Kobus Jooste]

Earl, I believe that in my response, I quantified what I believe they should have said.  If this is how you interpreted it, I'm happy but it was not how I perceive it to be written. Expert advice should not look like a creative writing assignment.  In the same way they set out to rubbish duckweed after a mess it made of their system, they now seem to be taking aim at worms in aquaponics.  I have been running a duckweed only system for the last 18 months or so, and even with the entire Lemna gibba batch dying off rapidly (around 3 kg of dead duckweed in under 4000 liters of water), I did not loose a fish. Now I can state with confidence that tilapia can take very low DO and even before you will see a fish do the smelly back stroke, you will notice their swimming and feeding behaviour change.  I could say that for duckweed to be left long enough to kill tilapia, someone was not paying attention, but that would not be nice.  Was it worth them going against what countless research papers and development agencies state about the potential of the plant?  In the same way, writing a big scary essay of sorts about worms in aquaponics when they do not operate media beds (????? or do they now?) when the essence of the message should simply be: beware of worms coming from feedlot cattle establishments and use your common sense with regards to manure and aquaponics, they get quasi biblical about the issue.

 

I recently had the unpleasant experience of sitting through a cut-and-paste presentation by an "aquaculture expert" who bumbled along rubbishing aquaponics as a potential development tool in South African agriculture because he could not make the UVI model fit the Malawian situation.  What upset me the most is that people who do not know better probably believed that man.

 

I have no problem with the common sense warning theory, but then they should qualify it as that.  They should also state what their experience is with worms in aquaponics (and why Australians have not been this scared of it ever) and why they felt it important to write what they did.  I could say that there seem to be anecdotal evidence of a lot of their high profile original designs being retrofitted with media beds, filled with worms.  This is not their design as I know it and it could just be that they do not like it all that much.  That is just my opinion coming from the other side of the world though and I am not stating it as fact but as a possibility...................