Sump filters are an excellent choice as they increase the overall volume of the aquarium. This means you have a larger margin of error as pollutants are diluted across a bigger body of water. I have noticed that some tank makers go for really complex sump systems with intricate baffles within their systems. They look great but are often difficult to maintain.
Our tried and tested sump setup is easy to install and maintain. It needs only one baffle to be siliconed in place. Many of our customers have used an old aquarium as their sumps.
Whatever you choose to use as biological filter media makes sure the water reaching it is as clean as possible. Poret foam will remove all the debris providing crystal clean water. We only ever use Poret foam as both mechanical and biological filtration. The bio filter kits we sell is made up of 5cm squares of Poret foam. We find this type of material does not need cleaning, no matter how much mulm covers the squares no loss of biological efficiency is experienced. This is very different from almost every other biological media. If you have visited our filtration design page you will know how important this mulm is.