how do i safely change filter cartridge?

[breezie713]

okay well i want to change my filter cartridge but i need to know how to do that safely without getting rid of necessary bacteria and with out causing my tank to go through a "bad mini cycle" please give me a thorough explanation on how to do so.
P.S: I ALREADY HAVE TRIED TAKING THE CURRENT CARTRIDGE AND RINSING IT IN TANK WATER.
please and thank you =]

[AngelMom]

Do not change any biomedia, just the foam/floss and carbon (if present). Changing filter mechanical/chemical media does not usually remove enough of the nitrogen eating bacteria to cause a mini-cycle, but with your tank being way over stocked and under filtered, it's always a possibility. You need at least a 40 gallon tank for the fish you have, and the filtration should be at least 1.5 times the tank volume (eg, a filter capable of filtering 60 gallons/hour for a 40 gallon tank).