It's a Inland Seas Suction Screen like my 6" x 1" npt clear on the right ,I also had a 3" x 1" npt is what I use for my set-up . I cut the end off so I could go all the way to the bottom of the canister filter and use a 1" npt coupler and a 1" pvc pipe for my out-put. I was able to push the mini bio balls thru the 1" ports that my filter housing has and fill it, Next time I'm going try with out them since the housing is over 20" long .
Thanks for the response! In my original post I said I didn't think it was the CO2, but you're right, it is. After I wrote the post, about an hour later my lights turned off for the evening, as well as my CO2. I noticed I no longer heard the reactor, so I went up to the tank and low and behold... no bubbles. So you filled the reactor with bio balls? What is the suction screen you mentioned?