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Re: [APD] Re: Co2 tubing and Light

--- Wright Huntley <whuntley at verizon_net> wrote:
> Vinyl tubing, as used for regular airline has
> plasticizers that will 
> interact with the CO2 with potentially undesirable
> consequences. Even if 
> those don't add stuff you don't want to the aquarium, the
> erosion 
> eventually hardens the tubing and may make it stiff and
> brittle over a 
> long period of time. [I've never seen that, but it has
> been reported, I 
> think.]

All plastics harden over time, some at diff rates than
others and some are more affeected by things like UV than

> Silicone tubing has long been used in hospitals as it has
> less 
> interactive chemistry, so is suitable for even oxygen as
> well as CO2 
> lines. Unfortunately, it is more rubbery and stretchy, so
> must be 
> attached to bayonet fittings with a wire tie, or it may
> blow off at 
> pretty low pressures. It also makes distant needle valves
> tough to 
> adjust, as the (slight) balloon must change size before
> the bubble rate 
> changes. It is also pretty damned expensive!

Some even say the silicone tubing is *more* susceptible to
CO2 than vinyl. I'm not making that claim; I'm just saying
it's out there, too. I think one would be hard pressed to
find a good example of either being a problem -- and by the
time it hardens, so what? replace it -- it's a relatively
small expense and we're talking years here at worst, not

In fact, it's hard to track back a source of the warnings
abut tubing except to vendors of "special" tubing. But I'm
open to more info.

> I think some semi-rigid tubing, like Clippard's and
> refrigerator 
> ice-maker line (polyethylene?) may be better for CO2 than
> vinyl, and way 
> cheaper than silicone.

Excellent point. The polyethylene works fine but it's a
little harder to work with and to route. I don't think
anyone should feel like they will have big problems if they
use ordinary airline tubing, or silicone tubing, or
polyethylene or polypropylene, or copper tubing. Long runs,
tubes buried in walls or passing through floors is another
matter -- then rigidity and puncture resistance is more

Scott H.

S. Hieber

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