Personally I have NEVER cleaned my ponds apart from scooping out a few leaves. My ponds are netted so not many leaves get through.
A multitude of pond life must inevitably be removed in the process of cleaning, some live in the sediment and help keep the pond bottom 'clean', some are food for other pond life, etc., etc., etc.
I allow the roots of oxygenators to spread in the 'muck' on the bottom of the ponds and this seems to help keep it 'sweet'.The frogs burrow under it in winter (they also hide in the liner folds)

However commonsense must prevail, and if sediment became to thick or 'smelly' from rotting leaves etc., then a clean up is obviously necessary to prevent poor water quality.

Also depends what sort of pond you want....I have a friend who removes all his fish every Spring (Orfe, goldfish, Shubunkins) drains the pond, scrubs the sides (it's a concrete pond) refills with water and puts the fish back as he wants a 'clean' pond!' eeeeeerm....I think this is excessive and he does tend to 'lose' a few fish each year!!!

Koi ponds are a different 'kettle of fish' and usually have bottom drains for cleaning.

my large pond is 5yrs old this summer,,,and every now and then i just run the net along the bottom,,so as not to disturb it too much,as well as keeping everything i see go in out! i try to keep as much off the bottom as poss,,,i did clean the smaller one a few times,,and boy was it nasty ;-)

What you say appears to make sense to me because my pond does not smell at all although I have to say that when I tested the water it came up with a Ph of 9.1 but then our tap water is 7.0
I think that I will buy a test kit that tests for all the problems but I suppose that then I will have to see what the results require that I should do if the Ammonia or nitrite levels are to high.

be careful about those kits,,,i never lost a fish in 5yrs,,,done a bigger pond,bought a kit and became obsessed,,,i then found this site and could not keep off altering things,, i check one or twice a year now,and just rely on my "babies" behaviour,,less stressful! ;-)

I agree with Anabel, when the pond has settled in properly the fish will tell you if something is amiss, the test kits will give a different reading if you use them an hour apart. Once you have got the biological balance right then, excluding unusual events, the fish will tell you if there is a problem.

hi
all.
im very lucky as i have a cat fish that keeps the pond bottom in good order ,he is about 17 inches.

----------DAVID-----------FISHMADUK--------------------

hi every one, i must say i do not like to use test kits or treatments from past expereince as you can cause big problems, and all so resulting to loosing fish. my pond is 13 foot by 11 foot approx 28 inches deep. so i have never treated my fish now for ten years and they are very healthy. i have had to make a bigger filter system and all so change the media as well, due to the smelling and green water. so now its all nice and clear.plz if you have any thing to ask about ponds i would like to help i dont know every thing but i do know some things..

Hi Baliol, is yours a fish pond or a wildlife pond? I think the majoriity of problems are in ponds where the fish are being fed, and there is over feeding, and a build up of ammonia or fish waste.
Mine are wildlife ponds, and I don't have any filters of any sort. One has sticklebacks, the other doesn't have any fish.
When the fish pond was newer I had more problems than now regarding water quality, and had to do a partial water change once.
Nowadays the only cleaning I do is trying to fish out dead leaves with a grabber (esp lily leaves) and occasional thinning of oxygenators. The ponds are quite overgrown at the moment, but the water is clear. When I pull out oxygenators by the roots there is sometimes a smell, but that's all.
I have various test kits, but have only used them occasionally.
I don't hoover my pond, and accept all visitors whether carnivores or not (apart from perhaps herons and ducks)