i have a juwel rio 300 tank with the internal filter taken out and an eheim 2126 external running at the moment. this filter is reccomended for tanks up to 350l but im having problems with particles in the water despite regular water changes up to 30% a week. my tank is not over stocked by any means. do you think i need to add another external filter and if so what do you reccomend. i was thinking of adding a fluvel 205 or 305 and filling it with filter floss.