Just have a question. I have tanks from 75 on down to 5 gallons. Can I operate any of them with just a sponge filter. Currently I have power filters on 11 of them and a canister (Rena Xp2) on my one 75 planted. I'm doing another 55 planted. If not can I use a power filter without carbon, say with just those microsponges. As I hear carbon in a planted tank isn't a great idea bc it takes nutrients out of the water. And would it be safe to remove the chemical media from my canister for the plants?