A powerhead by itself won't filter the water, it will just move it around. Typically, a powerhead is attched to an UGF
. Since this is going to be a planted tank, I doubt you would want one of those. I've never done a planted tank so I may be wrong, but it makes sense to me that way.
You'll probably want to use a HOB
filter. Everybody here has there own preference as to brand (I like biowheels, so I buy Marineland), but you'll want something that will filter the tank about 6 times per hour. In your case, something that pumps water at 300 gph