This may have been asked, I didn't see it though.
What type of cartridges are in your filter right now? If you have carbon cartridges, you do eventually change those, but not the floss or sponge stuff. If it gets gross, swish it in some old tank water when you pull a change. it'll knock the nasty sludge off, but won't hurt the beneficial bacteria that are growing in there.
Hopefully, your tank comes around soon!