Actually I would suggest something a little different. Depending on the configuration of the HOB
, place the new sponge infront of the old one. Basically, water in>>old sponge>>new sponge>> water out.
That will seed the new sponge faster. It will slow the filter down a bit for sure but the new sponge will gain the necessary bacteria much faster while not becoming detritus saturated in the process.
Might need a powerhead in there for surface aggitation during the switch.