Find a way to hang the old filter media in front of the return.
Might be a bit messy, but it'll help seed the new filter media (as it picks stuff out of the water) and will baffle the flow on the return, and you can do a thorough gravel vac in about a month.
Might be a bit messy, but it'll help seed the new filter media (as it picks stuff out of the water) and will baffle the flow on the return, and you can do a thorough gravel vac in about a month.