Aquaponic Gardening

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rubbermaid stock tanks not NSF approved

I have been locking into aquaponics, and have seen people online suggesting using rubbermaid stock tanks! checked with manufacturer tanks are not approved for human consumption. may leach chemicals BPA, and others into water. I don't understand it's O.K. for your livestock but not you! I dont think they should be using it for livestock! afterall don"t we eat the livestock?

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Comment by Tom Bilderback on September 22, 2015 at 5:06pm


First time on the site so grace appreciated. Im just gathering parts no running system in my life as of yet but noticed this tank discussion. I have a place that offers 275 gallon square IBC totes for tanks. They even say for aquaponic farm use. Has anyone had experience with these before?  

thank you, 

Comment by TCLynx on August 17, 2013 at 10:37am

A lot easier for anyone who is using it as a water tank to swap them out, and the fact that water alone is far less likely to cause this deformation.

Now I don't have the degree in engineering (audio engineering is more an art/technician sort of line of work unless you are talking about designing the actual equipment.)  Anyway, in laymens terms, think about filling a tote or container with water, to illustrate the idea better think of one of those softer roughneck storage bins.  With just water the bin may bulge out a little when full but it can relax back to it's normal shape when drained.  Now if you fill it with heavy gravel, it may bulge out a little when first filled with that gravel, and then every time it floods with water, that gravel is going to shift just the tiniest bit to try to bulge the tank more.  Then when the water drains, the gravel is there wedging the bin so it can't flex back to it's original position and this continues every hour of every day for years and sometimes the sun is going to be heating that plastic as this happens and sometimes cold is going to be chilling the plastic. 

So is it any wonder they might occasionally give way?  NO

I agree we are putting these stock tanks under very non-standard stresses.

AND yes, manufacturing irregularities are going to happen, especially in injection molded plastics of this kind of size.  The fact that they can produce these tanks at such a price is actually really impressive considering the cost of the equipment, molds, and electricity needed to run them.

It is a pain to replace a media bed of any sort just because they are usually full of media, plants and you have to bypass the water going to them some how while you do the work.  But just about any type of grow bed I've seen could experience some sort of problem over time and need repair or replacing.

Now supposedly the HDPE tanks could be heat welded to seal the leaks.  I don't expect such a thing would be advisable to trust to heavy gravel again but I use the 100 gallon stock tanks for so many things......................

Comment by Meg Stout on August 17, 2013 at 9:45am

In my experience with stress analyses using tools like finite element analysis, that bottom area is the one that would be subjected to the greatest stress over time under the load of internal weight. The technical term for the result of that stress is plastic deformation - in this case, literally plastic deformation. It's also called necking, when the material actually parts (splits).

It was fun writing home my freshman year of college and telling my family I'd had a class on necking...

UV embrittlement would certainly affect the location where the deformation/necking would occur. Though that might not be more important than manufacturing variability in the wall thickness. For what it's worth, the change in stress associated with the flood and drain cycle will fatigue the tank at the inflection point - kind of like how it's super easy to break a paper clip by wiggling it back and forth.

Again, I suspect it's not worthwhile for the tank manufacturers to run this to ground. We are using these tanks in a non-standard manner. And at $70 a pop, it's not that expensive for a farmer to replace a ruined stock tank in his/her fields, were that to happen.

Comment by TCLynx on August 17, 2013 at 9:21am

The tendency for flood and drain media to manage to bulge out all sorts of containers means that it can be really hard to find a rigid plastic bed that isn't going to experience problems in the long run.

I think perhaps the "box of rocks" idea there may possibly help (though I'm not sure it would guarantee it and maybe not for the reasons we would expect.)  It would protect the black plastic bed from sun.

As noted the beds I have had crack are filled with the heavier somewhat smooth gravel, they are flood and drain, and the location that cracked is near the bottom just inside of where the "feet" are where it kinda curves in to the waste at the middle.  They cracked on the WEST facing side.  I patched one temporarily with that two part epoxi water weld stuff but it started leaking again later and developed another crack so I removed that one from service as a media bed.  It is now acting as a worm bin mote with only a few inches of water in it.

Comment by Meg Stout on August 17, 2013 at 8:59am

I wonder if the cracking would have been prevented if the bottom 1/4-1/3 of the tank had been buried in supporting media. Say if the tank in question had had a box build around it and filled with sand or rock, to equalize the stresses on the material.

It won't save any tanks already split, but might save tanks an the way to splitting... And even if the box materials degrade (I know you have crazy aggressive termites down there), it could be rebuilt relatively easily without subjecting the grow bed itself to much time without that extra bit of support.

Comment by TCLynx on August 17, 2013 at 8:48am

the rubbermaid stock tanks do not have any certifications saying the are food safe so no one is ever going to be able to give you a certified answer that they are food safe.

They are certainly safe enough for livestock water and feed and I can tell you they are definitely fish safe. 

I have now found that the 100 gallon stock tanks when used as grow beds with heavy gravel doing flood and drain, some do start to crack near the bottom after about 4 years or so of use.  I haven't had any with the light weight media start to crack yet but I have had two that had the heavy brown river rock develop cracks.  Sigh.....

Comment by Gail Panzitta on August 17, 2013 at 8:36am

Hello all!

I just purchased a 300 Gal Rubbermaid tank then saw this forum with the concern whether or not they are food safe, which sent me doing some fast research. 

I found something you (those concerned) may be interested in; a forum for turtle owners that are talking about the same topic: 

One of their members has made "The Ultimate List of Stock Tanks" which is maintained by their group- pretty impressive. If you read through their posts, their research seems to indicate that the black  Rubbermaid tanks are food safe. Personally I'm going to go with the tank. My 35 year old horse drank out of one and lived a pretty long life, not dying of toxicity (a dog ran him down in the snow and he broke his hip- had to be put down.)  

Comment by TCLynx on August 3, 2013 at 2:15pm

I agree.  And to go off topic with you

My opinion is that everyone must form their own opinion.

Now food-safe materials is not necessarily the same as insisting that all materials be "food contact" certified by NSF or be made of FDA compliant materials.  And heck, with the aquaponics we really must go a step beyond since it has to also be fish and bacteria safe too.

Sorry to hear that you have a troll beating you up over on YouTube about it.

I too think it is kinda crazy to have GAP and GHP auditors deciding that having fish in an aquaponics system is equivalent to spreading fresh manure on crops when there are agricultural fields that spray plants with raw river water (that by the way has fish and therefore fish waste in it as well as perhaps having dead animals, manure run off, perhaps even human sewage runoff) and that they consider fine.  But the idea of using potable source water and fish being fed pellet fish food and being careful not to contaminate the system with any likely pathogen sources should cause anyone to fail an audit.

Heck, I believe I read some where (the rule sheet for some auditor or another) that if the growing area or processing area, HAS or HAS EVER HAD human or animal waste in it, that it is an automatic FAIL.  But they fail to define "ANIMAL"  Does this mean if your lettuce growing operation has ever had a caterpillar (and therefore caterpillar poo) in it that you are automatically failed from ever passing the audit ever again?  Does this mean that any and every organic farm that has earthworms in their soils is automatically failed from ever passing an audit.

I personally have no intention of ever even trying for a certification that would require me to lie and say there are NO living creatures ever present in my growing operation.  The whole point of Aquaponics and organic growing is that IT IS a Living system.

Sigh  AND the fact that most of the panic and knee jerk new regulations that try to stop things like aquaponics because there is fish poo in it, doesn't address the actual problem or where most of the food borne pathogen outbreaks come from, (which is most often in the processing and wash/handling water in large scale industrial operations.)

Comment by Meg Stout on August 3, 2013 at 1:04pm

I bet if you roughed up the interior surface of your HDPE tank the Thoroseal stuff would adhere pretty well.

I'm just getting beat up over on one of my videos from two years ago by nosuca99 stating you (TCLynx) are merely stating opinion and that Murray and Gary are adamant that one ought use food-safe materials, and that they may have said the stock tanks leach (no citation) and that fiberglass is best.

As for me, I'm much more concerned that global food safety standards prohibit the practice of growing food in the presence of manure (the global standards that all major food manufacturers are relying on for the safety of ingredients in their food products) and we don't yet have scientific consensus sufficient to convince folks that using water in which fish swim to irrigate our aquaponic crops isn't the same as "growing in the presence of manure."

Separately, there are ecosystems that have been in existence for over 200 million years (google search on Churince) that are being sucked dry by "traditional" agriculture to grow things like tomatoes.

I'm off-topic, I know. But it's frustrating having someone snipe without providing references, particularly in light of the issues you mention.

Comment by TCLynx on August 3, 2013 at 11:54am

Meg, any idea if either of those coatings would actually adhere well to the HDPE plastic of a stock tank?  I would fear that it would tend to scratch or flake off especially if used for a grow bed.

Again, the NSF and FDA don't consider some of the BPA or some of the other things we don't want in our food to be that BAD so there are plenty of "certified" or "approved" products that DO leach these things.  Much of our canned food we can buy at the grocery store is in cans lined with a plastic coating that DOES leach BPA!!!!!! 

So, just because the stock tanks don't have certification, does not mean that they do or do not leach or have BPA in them since it is quite possible that even if they DID have some sort of NSF potable water of food contact certification, they could still leach BPA.  And on the flip side, just because they DON'T carry the certification, doesn't have any bearing on things like BPA.

I agree with Robert in that if they are leaching BPA I don't want to be using them for my livestock either.

Now alot of those plasticizers are actually used to make plastics more supple or flexible or provide UV protection or whatever so I don't necessarily expect them to be in a rigid structural foam.  But, since rubbermaid doesn't want the certification, it might be as simple as they don't want to pay extra for it and the testing involved Or they may sometimes change their forumulations or use things in the process or in the plant that would stop them from getting the certification.  It is really hard to know how safe or dangerous any of those things might actually be.

I do know of people who used rubbermaid stock tanks in a system that was only using materials that could be organically certified.  That is not the same as "food grade" but are you certain that your pump is "food grade"  What about the jacket on the power cord?  What about the gasket on your bulkhead fitting?  What about your Uniseal (no the uniseals are not food grade certified and neither is the Duraskrim Liner.) 

Wait a minute, is your coir or peat or gravel or clay balls certified food grade? NO.  Neither is soil or dirt that grows traditional food.

The point is to try to choose materials that will impart the least amount of bad stuff to our food while still letting the good stuff work.

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