Adding old media to new filter?

I'm replacing my AC 110 with a Rena XP4. The AC has the sponge and a bag of biomax in it. I'll be putting the old biomax in the XP4, but do I need to add the sponge too, or do you think I would be ok without it?

 

Because you have a fully stocked tank, I would add the sponge too. You can cut it to fit.

Looks like a beautifully stocked tank, I might add. Any pics or videos?

 

I would add everything from the old filter, to the new, for a few weeks....and sponges usually hold most of the bacteria as they are more absorbent and easier for it to ad hear to

 

Biomax has faaaaaaar more surface area for bacteria than a sponge does. By volume, sponges don't hold that much bacteria - it's mostly open space.

 

Ok, I'll add the sponge. Thanks!

There are some somewhat old photos of the tank here Jaysee:

The stock and plants have changed a bit since then though and I'm planning on changing it even more. My pearls are extremely skittish and I think it might be due the bright lighting from having 4 bulbs over the tank. They hide under the plants all day, so I'm going to be adding lots of floating plants and changing out the stems that probably won't be happy under the floaters for lower light plants.