Filter too small?
So I just purchased my first canister filter! It's an Eheim 2211. I am going to install it on my 25 gallon which likely only had about 20 gallons of water in it due to substrate, driftwood, etc. I see that the 2211 is rated for tanks up to 39 gallons. However, I've been researching an only getting vague answers. Most say to err on the bigger side. I'm currently running an Aquaclear 50..
The Eheim 2211 is certainly an upgrade, isn't it?
What do you guys think?