so i just put in a emperor 400 power filter in my 55 gallon tank and also a penguin 200 in my 29 gallon tank tonight. in both tanks i have a established sponge filter. i kept my old power filters in the tank also so i did not loose any bacteria. how long should i keep the other power filters in the tank???? do i need to keep them in the tank since i have a established sponge filter in it. thanks for reading my thread and i hope u can help me out