I have read that ppl use their canister filters as a reactor, instead of bothering with building one. What are the downsides to doing this? I was thinking I could just run a t connector into the intake of whatever canister I get, & just run that by itself. Is there a downside to that? Less equipment to buy or make, & the filter would have plent of material to break up the gas.

Thoughts?

I have done this is the past with moderate success, if you want at least 100% desolution of C02, build a reactor, it is well worth it, and not hard at all, unless one is all thumb's
The filter will accumulate air bubble's using it for a reactor spitting bubbles into tank alot, also not good for the impeller in the long run, if you have a good filter, do yourself a favor..check this out v

http://www.aquaticscape.com/articles/co2reactor.htm

Craig are you running yours like the article you posted on the filters “intake” side? Seems to me the bio-balls will clog big time.

I run all of mine of the return side, you are correct the intake side would make it really grungy