Chemi-Pure works well but is expensive on an ongoing basis.
It needs to be put in some type of media filter, such as a canister filter.
IMO.. just a combo of some phos-ban and reef carbon works just as well.
You do have to be careful though with these types of products that you don't remove too much essential minerals from the water.
I usually use the recommended amount of phos-ban and half the recommended amount of reef carbon mixed together and replace it every 2 weeks.