I’m starting a new aquarium and just wondering if I can swap the filter sponge from my current aquarium with the one from my new one to speed up cycling, is this possible? And will my already cycled aquarium be okay with a brand new sponge?
I would seed the new sponge with your filter first before removing the old sponge. Might take a few weeks to do. If you remove the sponge from your established tank, and that's the only sponge in that tank, you could risk crashing your established tank.