Eheim filtering question?

[cirionrc]

We have a Eheim 2217. We recently took out the carbon pad and replaced it with chemi pure. The filter did not come with any maintenance. How often do you clean the media inside it. How do you clean it without killing the biology inside it and when do you do it? How often do I change the flosses? Also, we just bought a 40 gallon hospital tank and won't be ready for about 4-6 weeks + 3 weeks for quarantine. What is the best method for introducing a new fish from the store without quarantine. A medicated bath? freshwater bath? And how long does it need to be in the dip. Any suggestions? And I think I am ready for fish. The tank in 4-5 weeks into cycling with LR. The Ammonia is at .020 and the nitrites are at 0 and the nitrates are at 20. The damsels and the hermit crabs are very healthy looking now. Is the tank ready for 1 fish?