This is the Fluval AC-50 HOB filter. Two questions:

1. The filter came with a bag of carbon. I switched that out, opting instead for a second sponge (see pictured). Is that OK or do I need to use that carbon in the filter?
2. The instructions say to have the bio-max media bag in the position pictured but does that really matter? Could I switch the second sponge and the bio-max media back to provide better filtration for the water that has gone through the filter and is about to re-enter the aquarium?

To be clear, there is a sponge underneath both the bio-max media bag and the second sponge on the right in the picture. I just opted for a second sponge above the included sponge instead of the carbon bag but not sure if I need that carbon bag or not.

Thanks in advance!