I built a 3000 gallon pond in my backyard. Its made out of concrete.
Its mostly a goldfish pond, about 20 fish, several water lillys etc..

I have a large filter(it uses charcoal like gravel to filter) but its
no use. The water is so dirty that you cannot anything.

I have used some products to get the pond clean, but none have worked.
My fish are not dying, so I guess the water is alright. But I still
cannot get it clean.

The water is brown in color, and there is gunk everywhere. The surface
is actually pretty clean, no leaves or anything.

Do I need to Drain the pond and start over?