An excellent water polishing filter is a vortex Diatomaceous Earth filter. It is a bit of a bear to prime, but nothing works as well IMO. There are certain beneficial microorganisms, like rotifiers etc. that are resident in a healthy tanks water that a DE filter can remove (DE's can even remove parasites, the filter is so fine) so my advice is to remove a couple of litres of water before filtering, then return the water after filtering to keep up the micro colony. HTH
umatrix, you might want to print out that website.. Sometimes websites just disappear. I learned of the Vortex when I first started checking in here. It really is excellent filter. I've seen many pet/fish stores use them.