Good pond managment means keeping good water quality. That means keeping things clean and clear. Not only do fish add destritus everyday to the water but plants do add a lot of debris to the system also. Dirt from the atmosphere is always falling into the pond. So cleaning the water is very important because this is a closed environmental system.
The best way to do this is of course is with a good filter pump but even that cannot get all the material that collects in the pond. First of all keep your filter and filter pads clean and clear so the pump pulls and collects the smallest dirt and debris. Clogged filter pads and filter pump lose their power as the dirt collects and the filter then is not doing its job and it can wear out your pump more quickly so a good schedule of filter pump and filter pad cleaning is the first job and should be done on a regular basis.
Heavy destritus and rotting plant material may not get pulled up in the filter pads and sits and collects at the bottom and can cause problems and depletion of oxygen in the water and create situations where disease can breed. If the water quality is not good then fish are affected and stressed and thay can contract disease easier.
A good vacuum hose is essential to help clean the bottom where a lot of stuff collects. A vacuum hose like the one in the photo above is cheap and easy to use. The one shown in the photo is a good one, it has a shut off valve close to the large vacuum and this helps when you get clogs where the large tube meets the smaller opening of the hose. This way you just shut off the valve, clean out the large tube and fill it with water again, turn the valve on and it continues the process of syphoning with out you needing to suck at the the end of the hose each time to get the flow moving again. Make sure though that there is no air in the vacuum so air bubbles do not go into the hose and stop the syphon action.
Vacuuming your pond also gets you closer and you are able to observe your fish and the evironment better. You can then tell if your fish are healthy or if they are stressed. Clear eyes, fins that are open and the edges crisp and not ragged, vibrant color and active movement are all signs of heathy fish. Closed fins, dull eyes and dull scales and sluggish movement means the fish are stressed and in need of something and that is usually better water quality.
I vacuum at least twice a week and take out about 20% of the water then fill it with fresh water from my hose. I have well water so I do not need to add any declorination chemicals. If you have city water you may have to use this type of chemical but with a big pond 20% water changes do not add a lot of clorine to the system. If you are worried about adding clorine and other chemicals to the pond then filling buckets or large tubs with water 24 hours before using it will help clear up the chemicals.
One more way you can clean the bottom if you don't yet have a vacuum is by using a large fish net that you can buy at any pet store. Run the net across the bottom lightly so not to damage your pond liner and scoop up the debris and add this to your garden. It does have a lot of nutrients that plants will use and adds organic matter to the soil.
A couple things to remember, the more you feed your fish the more waste product they produce. Any left over food will also add problems to your water quality. So missing a feeding does not harm your fish and they will pick at algae and plants when not fed. Missing one feeding will also get them very active when you do feed them next time.
the more fish and plants you have the more you need to change the water. overloads of fish does stress the water quality more quickly so a good cleaning schedule will alleviate any problems from cropping up.
Plants do add oxygen to the water during the day but at night that process reverses and you may see your fish at the top guppping for air in the morning. Make sure your pump is creating a lot of bubble action and this will help keep the water oxygenated and flowing through out the pond.
well, I hope this helps you with your pond.