I'm thinking about using a canister filter to force water through carbon and or purigen. I figure I would get more effective water to carbon contact if the water was being forced through it instead of having the bags float around in the 3rd chamber of my Biocube29. I wouldn't use filter pads or anything as I don't want to worry about the thing getting clogged. What do you guys think? Additional water volume also couldn't hurt?

Not a bad idea. Just make sure you clean it out every so often especially if you have a big bio-load.

I've been thinking the same thing. Let me know which one you get and how you like it. I currently have an xP3 but it's too big and difficult to maintain. I want something smaller to "polish" the water so let us know how it works out.

You can do that for sure. Alot of people use canisters as media reactors. Just make sure to keep it clean.

I have a fluval 405 that I am going to put on the Finnex 30. Adds water volume and bio/mech/Chem filtration.

I've been thinking about a Fluval 205. I don't need the circulation but want the mechanical/chemical filtration. I also like that it's smaller. The xP3 that I have isn't that bad but it's just so big and it's kind of "wedged" in beside my sump and maintainence is a real pain. The 205 seems just right in terms of what it can hold an size-wise.

I used the rena filstar3 on my 29 bio.worked real good if you like strong flow.I ran it full fo live rock with carbon at the top. I hae heard some people that split the return in 2 som as to cut down on the flow of the return a little but all in all it worked out great.