hi i have a juwel rio 125 going along fine water stats are fine are in the process of running a internal filter with the juwel filter hopefully taking out the internal filter just leaving the juwel filter the ? is are juwel correct about changing the sponges that frequent ?or are they just after your money ? the white poly pad definately needs changing weekly as it is filthy but what about the nitrate & carbon sponges and all the other sponges ? any help would be gratefully received