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CO2 - tubing and filter questions

    I just started using compressed CO2 in my planted aquarium after an
equipment upgrade this year.  Prior to this, I read about CO2 for a year in
rec.aquaria.freshwater.plants .   I also did some reading (via google
searches and searches at actwin.com) before assembling the system.
    An area that I have seen much contradiction in what I read concerns the
effect of CO2 on vinyl hosing and silicone hosing.  I have read that 25% CO2
loss can occur in hosing, although some references attribute that loss to
vinyl and some to silicone.  I do not understand how a percentage can be
expressed when flow rate is not taken into account.  For example, if I drain
my entire cylinder in 5 minutes via vinyl hose, obviously 25% of the
contents would not have escaped via the hose.  So my question here is, how
much CO2 actually escapes through the hose at the low pressures used for the
aquarium (or is that the 25% figure)?
    My second question concerns hose cracking.  I have heard that vinyl hose
will become brittle after long term exposure to CO2 and it is best to use
silicone, I have also heard that silicone will crack and it is best to use
vinyl.  I am wondering which is correct (if either).  I am hoping it is
vinyl that cracks otherwise I might have concern for the seams of my
aquarium.  In addition, I inject CO2 by sending it into the intake of my
brand new Eheim Pro 2 (anyone else have priming problems with this filter?)
and am wondering if whatever effect is causing the hosing to get brittle
will cause my filter's hoses, gaskets and other rubber and plastic parts to
get brittle.

Thanks for your time,