Just stumbled across this thread and wanted to share my experiences with plant filtration. My wife and I have been raising an Mbu puffer as well as some Tanganyikan cichlids for about three years. We have moved tanks several times during that period but always had emergent plants as part of the tank, for both security for the fish (the plants' roots..) as well as aesthetic reasons.
This is the stock tub they were living in while our house was being remodeled...
Filtration in that tub was just by the Peace Lillies Roots and a couple of canister filters. Towards the end of the run with that tub, I tested the nitrates at one point and to my surprise, they registered about 40ppm. I says "surprise" because we were so busy with the remodel that I maybe had time to do a water change once a month and it had honestly been 2-3 mos. since I serviced either of the canister filters. Our puffer is 26" long and eats two whole crawfish a day, if that gives you any indication how much organic waste was going into the water and how much the plants were pulling out.
Here is the new setup, a 300G...
This is the setup for the plants...
...The two baskets in back are for the Peace Lillies and clay beads are used as the media. The black eggcrate in front is for the cuttings of Pothos, parrot's feather, etc. The two wire grates on the sides are for other plants such as orchids and bromeliads, which do not want to be in the water but like the humidity from below.
The tank's primary filtration is a wet-dry but after my positive experience with the plants, I would not do a big tank without them. Here is the build thread if anyone is curious...
http://www.monsterfishkeepers.com/f...ka-quot-300G-build-for-our-26-inch-Mbu-puffer