It should be more than adequate (correct me if i am wrong guys) 10x turnover is a lot. From my experience the Fluval Underwater series aren't very good. (Had a U1 in a small tank and it stopped working every time it got the slightest amount of gunk in it.) If you are going for a Fluval go for the 2+ because I have one and it does a great job of filtering my 40l (It is actually to big for 40l but I have a fair few fish in it.) It is reliable and easy to clean.
As I said if anyone has experience to the contrary then say.
Hope this helps,
Tom.