I have a 5.5 gallon Fluval Spec V aquarium for my future betta. It came with a filtration system that consisted of a foam block, with carbon filtration and biological filtration. I was thinking about buying another set of biological filtration at PetCo or something like that. Should I need to use the carbon filtration in the tank? I don't really know what it's for and I've seen people who didn't use them. Thanks and PLEASE add any additional tips or advice.