Ive got a used filter that came with my 29 gallon kit that I want to use with my emporer 280. But it dont have the spongy filter in it? It has the carbon just not the other thing that the bacteria grows on. What can i use to replace it? And is there anything else I can use for a filter besides carbon? I know you all put some of your own stuff in there, im just new to this and dont know what to use?