There are many different filtrations systems on the market from trickle to pressurized 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.