The problem with the blue cartridges is that you have to replace them because they fall apart, and they have carbon. The reason neither of those are good is because you want to keep the same media because it builds up beneficial bacteria that if you lose can harm the fish. Also, the carbon is built in, so if you need to dose meds, the carbon HAS TO be removed, and if you remove the whole cartridge then you lose your filtration. The filters I mentioned can be customized, and have much more filtration options then the whisper.