Hate to tell you GodFan but ponds need spring and fall cleaning at least. We have 2 ponds and a steam. The biggest pond is 4000g and we have a pond vacuum. We do 2 or 3 large WC's from spring to late fall. A lot of muck, leaves, and other things fall to the bottom of ponds raising nitrates and phosphates. Not all ponds have filters either which makes periodic cleaning very beneficial. Plus depending on the type of fish dictates what types of plants you can use. Koi such as we have are plant eaters so even marginals are hard to use as they eat and pick at the roots. Larger floater such as water hyacinth and water lettuce work.
Ponds are very different than tanks as already stated and don't make for good comparisons in this instance.
Hmmm... I dont know that I want a pond then anymore lol