Best filter for a 20g

[rvm]

I've just got a 20g tank that came with a fluval 2+ internal filter, and I've had a fluval 4+ knocking around for a while that came off my main tank when I changed to a cannister.
I'm going to put my pair of sajicas in the 20g along with my platies and neons, but I'm not sure if the 2+ is up to the job. It looks really small!! The 4+ only just fits in the tank, so I don't really want to use that.
What is the best type of filter to get. I was thinking of splitting the difference and going with the Fluval 3+, but thought if I sell the 2+ and 4+, I could probably afford a small cannister like a fluval 104.
Would I get a significant advantage with the 104 over the 3+???

 

[fishlover900]

My 10g tank has a fuval2 in it. This seems a bit to powerful and takes up to much room. If the box for the fuval2 says it suits your tank you will be fine. Just don't overstock your tank!

 

[rvm]

I does say it is OK for a 20g. But I like to overfilter my tanks, hence the reason for wanting an external over the internal. Also I prefer the flexibility in terms of media of externals. I'm pretty much decided that that is the way I'm going to go. Thanks for the help though!!

 

[K-Holed]

Eheim ecco canister filter, I've heard good things.

 

[rvm]

I was going to go for one of those, but I came across a Fluval 204 for £25 on eBay, so I got that. Problem solved!!! Thanks guys