Hello all. About a month ago my son got a TopFin starter kit aquarium for his birthday. The tank has been coming along quite well. I've never had a tank before and I think it's time to change the filter cartridge. I'm just wondering exactly how to do it. I'm afraid if I just change it out with a new cartridge I will lose a lot of the cycling work that's already been done. Can anyone please tell me how I should go about changing the cartridge so there is as little detrimental impact to the tank as possible? Thanks a lot! BTW - I think the filter cartridge needs changing because it looks like there are little dust particles coming into the tank. The water isn't cloudy, but it's not as crystal clear as it's been. Thanks again.