degassing aside, get a canister. They are simply better. They aren't as noisy, you lose less water to evaporation, there is more filtering media. the only downside is that they are a pain to clean. But that is all but made up by the fact that you don't have to listen to it splashing ever three days.
What a debate. I haven't nothing against canisters, but when my CO2 is working, I get about 15-20 ppm of CO2 with my HOB (AC-50 on a 29 gallon). I do water changes once a week, and my water level has no visible drop after one week.
I agree with the canisters make less noise, though that may be caused by my keeping it under the tank, inside a cabinet. Since I keep an open top tank it tends to get a fair amount of evaporation regardless. I am also able to keep the tank closer to a wall than I was using my HOB's.
I do have an HOB on my 10 gallon tank and an internal bubble box filter on my 5.5 gallon tank. And I do like them all. My HOB tends to get cleaned more frequently as I can just pull the media out without shutting things down, whereas the canister does need to be shut down. All in all it is still easy to clean.
I don't think you can go wrong with either choice, so get whichever will suit your setup and budget.
I recommend the Eheim Classic 2213 Canister Filter. Provides great filtration, flow, and is quiet. I've purchased several 2213s for my tanks, and love them.
If not, Rena Filstar XP1 or XP2 are good alternatives.
See if you can find a deal on a fluval 204, they are like 1/2 price since the 205's came out and I love mine it was $55 at foster and smith online). 205 looks the same only black? not sure what other differences are in it but it looks the same to me. I think it is a bit much for my 20 gallon, and would probably be perfect in 30-40 gallon.
after dealing with my aquasuck filter I think I'm a fluval fan all the way!
id love to own an eheim im sure they are very good but I feel they are overprice (no experience with them though)
I have heard that the eheim are more reliable, but i've only had my fluvel for a year, so I don't know what an unreliable filter is yet. But I do like my fluvel.
A definate no on the Eheim Ecco, people who have them have regretted the purchase and wanted the Classic since it's better, easy to prime, good flow.
The Fluvals are a good alternative, quiet higher flow rate...negative are the ugly gray attachments, jet flow, and no spray bar..
The Eheim 2213 or the 2215 will be best for you. I personally would just go with the 2213. I have it on a 29, works great. But if you want the flexibility of extra flow go with the 2215.
