why is my pond brown and not clear

hi i have 1050 gallon pond with two waterfalls, two pumps and filter boxes, but it is brown and not clear. pond has about 30 fish from gold fish, orfe and koi. it has marginals but have never been able to grow oxygenating plants get eaten too quickly. have a water lily. plus even though it does not have any overhanging/ shaded sides on two of them i never get any flying wildlife like damsel or dragon flies. do have frogs.  what advice can you give me? 

How is the pond lined - clay/plastic? Could the waterfalls be disturbing the sediment at the bottom of the pond/ Does the pond get enough shade from the sun?

I asked hubs, who was always a keen pond and fish man (until last year) and he said

- Have you got soil in the pond?  Not a good idea with Koi as they are notorious for digging around and disturbing the soil.

- Are the filters large enough for the amount of water you have and how often do you clean them out and at what level is the water taken from the pond?

- Have you an ultraviolet light in the filter system which kills the algae?

- Have you tried putting your plants in baskets lined with hessian to keep the fish away from the roots?

- How much of the surface area of the pond is shaded by plants?  At least one third should be shaded.

- Do you feed the fish?  Don't leave uneaten food after 10 minutes.

- Do you have visiting ducks?

I think that's enough to be getting on with but if you could give as much information as possible he'll be able to help you.

Am new on this site....hope its ok to comment.  my son has a small pond and it too isnt clear but as you mentioned it should have a third shaded, then l will let him know. thanks for the tip Robot  and l hope too that you Linda get it sorted. 

Brown water is an accumulation of suspended particles caused by organic matter.

There are far too many fish for starters. That size pond should really hold 17 fish max.

Using the old rule-of-thumb of 1″ of fish per every 10 gallons - 15 fish at 7″ (for example) comes to a 1050 gallons pond.

How long has the water been brown, when did you start having problems ?? And how long you had the pond ??

From my experience you will never have truly clear water if you have Koi, they distrub the bottom all the time and your pumps them distribute the particles throughout.  One positive is that your brown water hides your fish from passing herons.

Please answer all of robots questions so either me or him can give you a detailed break down on what to do next...