Yes, but to a lesser degree for planted tanks. Whether you absolutely need a filter will be a function of the amount of flora you have and the proportion of flora to fauna. Erring on the side of caution, most folks would probably tell you that you should have one.
In a heavily planted, lightly stocked tank with relatively fast growers, it's less important. In fact with many hi-tech tanks, filtration servers almost equal parts in removing harmful ammonia and nitrites as it provides circulation for proper fertilizing and CO2 distribution.
However, without knowing specifics, I would recommend that you do have some sort of a filter.
Last edited by STS_1OO; 03-07-2014 at 02:37 AM.
Reason: more info