i have tried breeding with both a sponge filter right from the start and i have tried it without a filter, both methods worked for me. i prefer not using a filter at first though because the water is treated with indian almond leaf and i want all the minerals etc. present in the water,more importantly, i also want the water as still as possible to initiate breeding. after a couple of weeks when the fry are swimming etc. then it's recommended to throw the sponge filter in.