Who Gives A Fish Forums

Exactly. Flow is key. I'd also recommend adding a bit of fish food to the tank to keep the bacteria fed while the new filter establishes. Just don't overdo it, or you'll get an algae bloom.

Yeah, and if you're impatient like me, you can always cheat and use a bit of substrate from an established tank. That stuff's packed with bacteria too.

Just remember to test your water daily during the transition. Better safe than sorry, especially if you've got sensitive fish in there.

And don't clean the new sponge for at least a month. Let that biofilm build up nice and thick. It's gross but necessary.