Maintaining ponds is the most important task you have once your pond is up and running. The amount of maintenance you need to do depend on many different factors like stock levels of fish and plants, size of pond, pond site, pond depth, the equipment you are using and so on.
Larger garden ponds keep a better natural balance so they need less inspection, cleaning and maintenance than smaller designs.
If you have overstocked on fish and plants this will cause problems or you need very good filtration systems in place and water quality checks need to be carried out more often.
If your pond is situated near trees or bushes falling leaves will sink to your pond bottom and decompose and give of noxious gases.
If you have shallow areas or shelves in your pond it will cause the growth of algae.
If you have inefficient equipment to keep your pond water quality up to scratch you will have problems coming your way.
On the other hand you could take the opposite of the above you will have very little maintenance, cleaning pumps, inspecting water features, cutting back or separating plants and maybe the odd bit of repair here and there.