DIY reactor question(s)

I am making a DIY reactor and have a few questions if anyone would be kind enough to answer
First off, I'm making it out of a plastic, cylindrical container that held plant fertilizer at one time. It is approx. 12" long and 3-4" in diameter. I bought some bio-sponge balls and put them in there ---- Is it a problem that the balls are smaller in diameter by maybe 1" than the container? Its not enough room to cram another ball in, but bubbles may actually sneak past the side(?). I was able to put 5 or 6 balls into it though.
My other question is, since this is not the common PVC reactor, attaching the thick tubes from my Eheim 2222 might be more difficult than I thought. I want to make an excellent seal, so I don't have a leak or hose pull out a few months down the road and have water spray everywhere. Should I just punch a hole big enough to feed the tube through and then seal it with plenty of silicon sealer and/or epoxy?? Maybe I should use a gasket or rubber fitting of some type, but I'm not too knowledgeable in this area. In the past, I simply fed the hose from the CO2 unit into a powerhead, which served as both the reactor and diffuser. This probably isn't as complicated as I'm making it, just looking for some advice. Anyone? Thank you.

-Ryan Ingram