Hi have you got or are you putting fish in your pond then yes you do need a filter box for aeration and keeping the water clear.the filter box i have has an ultra violet light in the lid as well.as soon as the pump starts to slow down is the time to clean the filter out it will tell you how to do this in the instructions.and no you are not being thick nothing wrong with asking.good luck.

Great thankyou! Off to find a filter, yes just got some fish in it, tiddlers at the minute