I have this tank: It uses these activated carbon cartridges: My tank has been active and happy for about 6 weeks, but yesterday the water flow pretty much stopped. I tested the water a week ago, and my numbers were great. 0 on Ammonia and Nitrite and maybe 5 for Nitrate, so I feel good about my cycle. But obviously I need to do something about my water flow. My assumption is that the filter media is clogged dirty and needs to be cleaned or replaced. I've tried to research this but I get so much conflicting information everywhere, and I'd like to make sure I do this correctly. I've read that I should change some tank water and use the old water to swish out my filter cartridges. Seems simple enough. But does that apply to the activated carbon filter? Can I just swish it around during a water change and put it back and move on? Or do I need to actually replace the cartridge like the manufacturer suggests? If so, I want to keep my bacteria, and I'm not sure how to do that. There are two cartridges, so I could replace one and wait a few weeks and do the other? Or is there a better method for this? Thank you so much for any help. I'm trying hard to treat my fish well and do things the correct way.