just for info purposes, it takes about 2 to 3 weeks to develop a good amount of bacteria. that is why i use sponges, i have some sponges that are several yrs old and still do the job. a quik rinse in old tank water during a
water change and they are good to go...you cna even do this weekly if you like, with no worries. if i do have to change out a sponge i cut it in half using half the old and the new, after several weeks change out the other half. so economically speaking the sponges give ou more for your money.