DIY CO2 reactors & vacuuming of gravel

Thanks to everyone who responded to my CO2 system questions in APD#202. My
system is now up and running (canister, regulator, needle valve, hose barb,
and airline to an Aquaclear 201 powerhead). The pH has gone from above 7 to
6.4 or so in less than two days, so I guess that means the powerhead method
is significantly increasing the CO2 level (if it doesn't, please comment).
Still, I'm interested in trying to set up a dedicated CO2 reactor chamber. I
asked about this in my earlier post and got some advice from a few people but
I still have a few problems. Specifically, if the reactor is made out of a
UGF tube or 1 liter soda bottle, how and where exactly is the the inflow of
water (via either a powerhead or the outflow tube of a canister filter)
attached such that the force of its' flow  doesn't seperate the two? Is it
generally just something that is jury rigged together with silicone sealent
and maybe some cutting/drilling, or even string? Or are there PVC type
fittings or adapters that fit the diameters of ugf tubes (1") or  soda
bottles on one side and vinyl tubing on the other? Also, I've briefly
experimented with using a strip of blue bonded filter padding as a "baffle"
in a UGF tube with a powerhead at the top firing into the cartridge cap, but
this seems to cause  too much flow resistance and the water mostly ends up
flowing right back out at the powerhead. I guess I should just try less of it
in there, but does anyone use something they think is better? Also, is there
any kind of DIY reactor that can be outside of the tank (more aestheticlly
pleasing). I guess that would rule out a powerhead as a flow source, so it
would have to be provided by my Magnum 220 canister. 

On another matter, my 55 gallon tank has one section of densely growing pygmy
chain swords. I vacuum my gravel as best as I can fairly regularly but I've
noticed recently that a lot of organic waste and detritus has accumulated in
and around the pygmys. It's tough to get it out of there because the plant
growth is so dense but I'm wondering if this sort of condition is bad for the
plants. I've seen some people say they keep tanks for years and never vacuum
them, but does anyone know about this? The plants seem to be doing all right,
for now at least, although there are a sizeable number of leaves in there
that seem to be going transparent (losing their chlorophyll).

                                Thanks for any help,

                                             Matt MacGregor