Hi, this post isn't really about bettas, more about my filter cartridge. I have a 2.5 gal Mini Bow tank with a mystery snail (apple snail) and anacharis. The filter cartridge gets really dirty and icky, and I'm wondering if I should change it. I know I shouldn't because there's good bacteria on it but I'm not trying to cycle the tank and I do weekly 100% water changes. I do wash it with old tank water, but it doesn't do much and that cartridge is NASTY. What should I do?