Eco (plant) Filtration
There are many different plant filtration systems around, this is a simple type of filtration for ponds of all sizes. Whist it is very Eco, they can require large surface areas to work efficiently.
There are many different filtrations systems on the market from trickle to pressurised all have there uses depending on the space you have available.
Aeration in a pond, do you need it, if you have fish in it then the answer is YES you do need it especially if there are a lot of pond plants in the pond, the highest oxygen loss in a pond is at night and this is taken by the plants. So having aeration during the night is crutual for the wellbeing of your fish.