do you use the carbon filter cartridge? I'm personally not a fan of those..one reason because when you change them out, it can mess up your cycle because you are removing the bacteria built up in it. I personally like to use the sponge filter media. It's cheap, it works great (it won't suck out any additives you put in the tank like plant fertilizers, etc.), and you only have to replace them when they are literally falling apart....which still has not happened to me yet. It has been years..lol
All you do with sponge media when you need to clean things is rinse it out in old tank water, plop it back in, and you're good to go!