I have a Aquaclear 70 HOB. I have had some suggestions on what to replace the carbon bag with after the first 2 weeks. I currently have an active filter in the tank from Angelplus. After a few weeks I was going to remove it and trim it to fit on top of the sponge that is with the filter already. So I would have the original sponge the active filter sponge and the bio bag. Would having 2 sponges and the bio bag cause an issue?