Aquaponics Digest - Sat 03/28/98

Message   1: Re: Safe plastics ?
             from Gordon Watkins 


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Subject: Re: Safe plastics ?
From:    Gordon Watkins 
Date:    Sat, 28 Mar 1998 10:31:23 -0600

Could you be a little more specific as to what sort of products you're
referring to, ie: piping, containment vessels, etc? 
        I have seen some indication that long-term use of pvc pipes can leach
toxins in closed systems. I'm not sure what suitable piping substitutes
might be. There are many choices for containment vessels including the
use of "inert" liners designed for aquacultural use. I personally use
poured-in-place concrete vats coated with aquacultural epoxy. I use some
pvc piping but I try to keep it to a minimum. I have also used old (50
yrs.+) wooden barrels made of cypress and redwood but the new ones will
slowly release tannins and probably other substances for some time. I'm
not sure of the toxicity of these materials. There are many types of
aquaculture vats available on the market made of different synthetic
materials which are supposedly harmless to aquacultured species. Hope
this helps.
                                        Gordon

bard@rof.net wrote:
> 
> Does anyone have information about the inertness of plastics, in
> relation
>  to using them for holding and transfering systems for aquaponics ? I
> understand that fish and plants do not seem to show any immediate signs
>  of illness due to the use of plastics, but has anyone ever compared the
>  effects of using 'natural' holding facilities, and transfering medium
>  to that of the standardized plastics-based systems ? Are there any
>  materials available that are completely natural ? What are they made
>  from ? Thank You