Sunday, December 23, 2012


There are several areas where toxicity should be considered.  Here are some questions to ask about the materials we use in our systems.
   Is our personal health compromised while working with a material?
   Will toxins pollute our food?
   Is it toxic to our fish?
   Is it detrimental to the plants?

Working with epoxy, or cutting, and heating OSB, Polystyrene, ABS, PVC all pose some degree of toxins so some precautions should be used during fabrication.  Most of the time our nose will let us know right away.  For example melting ABS is so toxic that it becomes nearly impossible without the proper precautions. Other materials like OSB or pressure treated wood may not trigger an acute response, but long term exposure to sawdust can cause injury.

Epoxy and silicon caulking and PVC solvent fumes are detrimental to our health, so precautions should also be used while working with them. After these materials cure the danger to us, our fish and plants diminishes to a level most would consider safe.   Silicone caulk comes in Type 1 and Type 2.   For our purposes Type 1 should be used because it is considered fish safe after it cures and is allowed to out gas.

Pond liners such as EPDM rubber, polyethylene, fiberglass, and polypropylene are safe for both fish and humans. Some people have used vinyl billboard material, but even when purchased new, this material can leach toxins.   Here is a link to more information about pond liners
"Pliable Vinyl was a bad choice for the water treatment industry, and water delivery systems (there's a reason it was banned for use in those applications... leaching of tetrachloroethylene, a really fun chemical) and it hardly seems like such a great choice for a re-circulating food production system.
Sure, mechanically it will work for a while (as long as you get a good one...btw, fun fact: calcium levels in your water can and does apparently affect vinyls pliability), but why someone would want to use even a 'virgin' vinyl liner in AP, let alone one rubbed down with things like ethyl ketone, silk screened, and set out to bake in the sun for a while, is beyond me.
IMO (as well as the International Agency for Research on Cancer) pliable vinyl in all its forms, seems like a really poor choice for such an application. There is a reason vinyl is called "the poor mans plastic". Both mechanically, as well as chemically it is an inferior product. There are not many plasticizers commonly used that will form a co-valent bond with vinyl, which is why they will leach over time. And is why vinyl is slowly being either outright banned, or voluntarily dropped from use (by industry) in many products/applications. "- Vlad Jovanovic
LINK to Forum
EPDM (Ethylene Propylene Diene Monomer): EPDM rubber performs well in colder climates. This highly flexible liner also resists air pollution and has a lifespan of 20 years. EPDM is also non-toxic to plants and fish and is stable when exposed to UV rays.

PVC (Polyvinyl Chloride): These liners are highly flexible, easy to work with and are UV stable if they are not exposed to direct sunlight. PVC liners last for about 10 years or more but are less resistant to freezing temperatures. But the safety off flexible PVC is suspect.  As Vlad has explained to me; (let me directly quote) plasticizers can and do leech out over time and make their way into our blood streams. Some of them are particularly nasty type of toxins. (Of coarse, those are the cheapest and most often used...again, particularly in the US). Here is a generic introductory wiki link on the topic that touches on some of the many health and safety aspects of pthalate plasticizers...

HDPE (High Density Polyethylene): HDPE liners are made from a tough thermoplastic substance that is safe for fish and plants. These liners are inexpensive and can last for up to 15 years. HDPE liners are the least flexible and do not work as well in colder climates. HDPE liners are generally less expensive than PVC liners.

Butyl Rubber: Butyl rubber liners are UV-resistant and last approximately 20 years. Some butyl liners can be toxic so do your research if you plan to have fish in your pond. Although somewhat flexible, these liners are thick and tough to fold at corners and curves.

Fiberglass: Fiberglass liners cost much more than flexible liners and are not as natural looking. Before setting a fiberglass pond in the ground, it is critical to use a thick layer of brick sand to pack under and around the pond. This information came from Home Depot

EPDM comes in different forms,  Some is intended for construction industry and then there is EPDM for ponds.  The difference as far as I can tell is that pond liner has been allowed to out gas by laying it out in the sun, but I may be wrong.  Use THIS LINK for more information on the wide variety of liners

Copper and galvanized pipe may not be toxic to us, but it should be avoided when fish water recirculates in your system.   Even your choice of heater element should be stainless steel in order to avoid poisoning your fish. I questioned this at first because our water supply often travels through metal pipe.  The difference is that we are recirculating our water and the pH of this water is generally lower than the supply.

Plants depend on minerals for their growth and iron deficiency is a common problem in aquaponics. The use of Portland cement in a fish pond or limestone in your grow bed will cause your water to maintain a high pH and thus deprive the plants of bio available iron.  Not all iron products are the same. Look for an Fe-EDDHA or Fe-DTPA product (chelated iron that is bioavalable to plants).   For more about this topic refer to this discussion


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