Hey there. This is a topic I'm going crazy over at the moment. As far as I can work out, wet/dry filtration is typically used for saltwater. Now, the guy who builds the tank/cabinet setups I'm going to buy reckons its perfect for freshwater tropical as well. BUT, a well known LFS told me that the wet/dry system (consisting of an overflow weir going down into a sump through a number of layers of filtration) will dissipate the CO2 from a tank - so its no good for a planted. (I know both of them want to sell me their setups as much as they can so I dont know who to go with on this one). If this is correct, and its not a good system for planted tanks, I'm thinking a good canister. But maybe you could use both hey? Because from what I've read, wet/dry is an excellent biological filter method. So , hopefully theres someone out there who's experienced in salt and freshwater and tried a wet/dry system in a planted freshwater tank!