My filter has the 2 parts. The Carbon filter and the bio filter. So if its best for a cycle to not change out either part is there a better thing I can put in where the carbon filter is or just keep the carbon one in there and hope it doesn't disintigrate. They don't look all that sturdy. I have the Aqua-tech power filter for 5-15 gallon tanks and my tank is 5 gallons.