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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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Although it has been asserted by several knowledgeable AP growers, it seems that it is not accurate to claim that fish cannot harbor deadly human pathogens. Specifically, Gordon A Chalmers, DVM, from Lethbridge, Alberta ( ; ; ) has published a study that states:


"There are very few reports concerning the presence of pathogenic
intestinal bacteria in farmed fish cultivated in unfertilized systems. Some studies
have reported Salmonella spp. in ponds holding catfish, and on the skin and in
the intestines of these harvested fish; the incidence was higher in samples taken
in the summer compared with those collected in the winter. In Japan, this
organism was found at low level in ponds holding eels, and in the intestines of
fish in one pond. Several organisms including Listeria monocytogenes,
Plesiomonas shigelloides, and Shigella dysenteriae (but not Salmonella spp.)
were cultured from hybrid striped bass (Morone saxitalis x M. chrysops) reared in
three freshwater systems in Maryland, USA."


In addition, he states: "Water can be a carrier of many microorganisms including pathogenic
strains of bacteria, such as Escherichia coli, Salmonella spp., Vibrio cholerae,
Shigella spp., and the microscopic parasites Cryptosporidium parvum, Giardia
lamblia, Cyclospora cayetanensis, Toxoplasma gondii, and the Norwalk and
hepatitis A viruses. Even small amounts of contamination with some of these
organisms can result in foodborne illness in humans."


I think we need to ascertain what conditions favor pathogens and what conditions will exclude them.

If fish are raised in water with large amounts of things like Salmonella, it will be found on and in those fish but the fish themselves are not the cause of the introduction to the system.


Now the fact that many reptiles can carry salmonella does kinda throw a wrench into the statement about cold blooded animals being safe for aquaponics.

Hmm, are they referring to aquaponic systems in stating, There are very few reports concerning the presence of pathogenic intestinal bacteria in farmed fish cultivated in unfertilized systems.?  It then goes on to state that Some studies have reported Salmonella spp. in ponds, so it leads me to question if the positive samples were then either from ponds and/or straight aquaculture and not aquaponic systems.  I am obviously not a scientist or a DVM, however I think we need to be able to evaluate aquaponic systems independently of aquaculture systems or ponds, where large fish populations are reared and typically there are disease outbreaks.  To my knowledge, outside of some occasional ick, which was introduced from new fish into a system, I do not know of disease issues in  AP systems.  Part of this I would contribute to the ecosystem balance of an aquaponic system and also to considerably lower stocking densities. Aquaculture systems are very likely to have disease outbreaks because of the incredible density and these fish are often treated with antibiotics and other drugs to both prevent and treat.  If disease is so prevalent in these scenarios, it would make sense that there would be a greater likelihood for these fish to carry other types of pathogens.  It would be interesting to find out if UVI ever had disease issues as they carry an incredibly high density.  I will see what I can find out.

Hey Earl, thanks for the great information.  So, what you are saying is that it is the GAP guidelines we need to see revised then!  Nothing like a good challenge, huh?  Is there anywhere else that it matters that the differentiation is not made or is it just the USDA GAP guidelines that will need to change?  When you say that they are not covered by the Code of Federal Regulations, are you inferring that there is no way to petition a change? 

Earl ward said:

 Hi Gina

The problem as I see it stems from the GAP( good agriculture practices) guidelines set by USDA AMS . In the GAP guidelines it does not differentiate, the difference between livestock and aquatic animals. GAP is a voluntary program, but a lot of markets require GAP. Aquaponics cannot pass a GAP certification, the GAP is all done by 3rd party auditors just like organic certification. So in other words the 2 programs are in conflict with each other Aquaponics can be organically certified  (7CFR 207.1))because it does not include Aquatic animals in the definition of livestock; but it cannot be GAP (USDA AMS) certified. One thing else I should mention Organic certification is covered by the Code of Federal Regulations which have the same weight as law and was open to public discussion before implementation GAP was not. Every 3rd party food safety audit I have incountered follow the GAP Guidelines.

Gina Cavaliero said:

Hi Teresa, thanks for getting Bob's opinion.  That is exactly concurrent with the circumstances surrounding Friendly's food safety certification.  They had the certification for their DWC system, obviously without worms, from the state of Hawaii. However when Costco insisted that a "third party" auditor, the state, was not allowed, they had Primus come in and test for the certification.  Just like Bob stated, The problem arises in the guidelines regarding animal wastes (in this case, worm castings and fish effluent) with regard to crop production, and proximity of said animal waste to the crop production.  This was the reason they were then denied their previously granted certification.  How the state of Hawaii as an independent third party allowed the cert in the first place, I don't know.  I would assume someone with enough sense to make the connection between fish being cold blooded and not warm blooded understood that the same rules that apply to traditional ag and growing methods would not apply in an Aquaponic system.  Unfortunately the auditors for Primus translate the letter of that law, so to speak, as literally as it is spelled out and have no flexibility on it whatsoever.  That only leaves us one alternative, IMO, the rules governing food safety certification need to change to encompass alternative growing methods.  So, what that means is back to the discussion that has occured here and several times on this forum, we need peer reviewed documents in order to present facts in order to enact this change.  It is all a big uphill challenge, but I trust that eventually our industry will make progress in that direction.   It will all take time, but the growth in our industry will be paramount to us seeing that change.  Have to throw in a plug here, we need everyone to join the new Aquaponics Association, so that those numbers can amount to a voice that will be heard!  :)

There are fish diseases that can show up in aquaponics (just like in Aquarium) but most of them can be controlled by keeping water quality high and not over feeding.  (Ick, columnaris, and a few others like fin rot or other bacteria that usually get called something like a fungus since people don't know any better.)

However, these fish diseases have nothing to do with the human food born pathogens made note of in the details about ponds.  I know that catfish grown in effluent heavy in things like salmonella and e. coli will test positive for those bacteria on their skin and likely in their gut from ingesting contaminated water and food but that doesn't mean that the fish will support extended survival of those pathogens.  (There have been tests where people were trying to figure out if they could grow fish in effluent ponds.)


About the only illnesses I know of that have much to do directly between fish/fish keeping/fish processing and humans are not food born but skin infections of the people doing the handling.


So our goal largely remains the same, we need to do some testing to see how long lasting different pathogens tend to be in aquaponic water and media.


In the mean time, good hygiene and washing hands before handling food or handing anything in the systems is just good common sense.

That is our number one defense against all pathogens.  Most of the pathogens if there are any will be introduced by humans.  

some one said that E coli could not live in an ammonia based system.  We strive to keep the ammonia low so that doesn't float.  

Back in 1998 the University of Hawaii published a guide ( titled: "On-Farm Food Safety: Aquaponics" and they give specific guidance for testing aquaponic water for pathogens. They state "Based on a statistically sufficient number of samples (generally not less than five samples equally spaced over a 30-day period), the geometric mean of the indicated bacterial densities should not exceed one or the other of the following: E. coli 126 per 100 ml; enterococci 33 per 100 ml." This guidance is referenced as being from the EPA for swimming beaches.


The FDA has published "Guidance for Industry  -  Guide to Minimize Microbial Food Safety Hazards for Fresh Fruits and Vegetables" ( While this is a guide, it is based on specific requirements in the US Code of Federal Regulations, which carry the weight of law. In addition, this is what GAP is based on. The specific Fed Regs are cited and information is given in appendix 2 on how to obtain copies.

While it is good to see that there are attempts to get some form of standards for production conditions and food safety in aquaponics, it is not entirely correct to use stuff such as swimming beach standards.  My suggestion would be to, as a first step, study aquaculture and hydroponic standards, and merge the best of these two sources.  From there, some work will be needed to clarify the conditions of media based culture

With all the interest in this section devoted to human introduced pathogens, I started thinking about UV sterilization again.  I have a UV sterilizer on in my bio-fertilizer research system permanently (permanent fight with algae), and even without media in the system, I have nitrates accumulating.  Thus, I do not subscribe to the theory that having a UV sterilizer in an AP system will harm the ability of beneficial bacteria to develop in the grow beds.  That said, I am not sure how effective it would then be to deal with introduced pathogens as the grow beds could then also be considered to be refuges if it offers the correct incubating environment. 


Thus the question: Would UV sterilization be any use in commercial AP, and if someone decides that they should be mandated, would it harm the functioning of a system?

Kobus, I have been mulling over the same things about UV for my tower system.  I'm not having algae issues but I know Nate has used UV on his systems, (I think he blamed it on a paranoia about plant diseases perhaps left over from hydroponic experience.)  Since tower produce is going to be primarily of the leafy and herb variety then processing aside if possible (negative) things in the water that might spray or drip off on the leaves then that would minimize most issues on the plants from the system.


Our bio-filter bacteria is primarily colonized on surfaces and therefore not in too much danger from the UV sterilizers.


One note though, a UV clarifier to combat algae normally functions a little different than ones meant to sterilize and kill bacteria.  While I think one that will kill bacteria will also do in algae, the one that is just designed to limit algae might not be very effective against bacteria.


In doing some reading, it seems that UV can also have other beneficial effects on the water for a system but none of this really addresses if there would still be "refuges" of bad bacteria hiding in the system somewhere and what sort of impact this could have on a system.

Great question Kobus.  Sounds like a whole new thread!  I started one on Green Acre's group page yesterday about the degree of Biosecurity we should be investing in.  Ultimately, there needs to be safe practices in place, but not to an extreme that would compromise production time if we are considering for profit operations.  There has to be a happy medium somewhere and I agree with TC and Raychel that it starts with good hygiene practices.  We just need to identify where the upper and lower limits of those practices lie.


Of course, much of this conjecture is based upon the fact that we simply don't know the facts as they relate to aquaponic systems.  It is great to extrapolate data from ponds, aquaculture, beach swimming areas and other applications, but like Kobus, I caution against applying the same criteria to aquaponics.  It is its own unique ecosystem  and demands its own set of parameters and results.  We need studies performed more than anything.

Kobus Jooste said:

With all the interest in this section devoted to human introduced pathogens, I started thinking about UV sterilization again.  I have a UV sterilizer on in my bio-fertilizer research system permanently (permanent fight with algae), and even without media in the system, I have nitrates accumulating.  Thus, I do not subscribe to the theory that having a UV sterilizer in an AP system will harm the ability of beneficial bacteria to develop in the grow beds.  That said, I am not sure how effective it would then be to deal with introduced pathogens as the grow beds could then also be considered to be refuges if it offers the correct incubating environment. 


Thus the question: Would UV sterilization be any use in commercial AP, and if someone decides that they should be mandated, would it harm the functioning of a system?

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