I think it depend on the type of pond. If it has substrate or not. I have a gravel bottom and I never really clean it. I have in the past cleaned other peoples ponds by draining the water re-fill, move the gravel around w/ my feet and repeat. This has happened twice one person had built the pond to low allowing dirt and mulch from nearby planting beds to wash into. I use a 100 gal. rubbermaid to save some of the water(if fish are present, to have cycled,aged water on hand). Same process as above with rinse and flush techinque. I also had a person w/ a rediclious algae problem cause by to much debris in the pond. Accumulation of leaves and full sun didn't help matters. This same pond had no plants growing in marginal areas or in the pond itself. Plants will help reduce the "silt" so long as the silt is not uneaten food waste. Silt from fish doo and dead plants will be used up in the pond itself as long as there is enough circulation to combat the decomposition. Hope this helps a little, but it all comes down to personal tastes (pond aesthetics). My pond little to no silt, at least it looks that way because it settles in between the rocks, is visible. If one was to stir the gravel it would show signs, but it clears up in a matter of minutes.