Some good information to have in your determination would what the depth of the pond is and how much muck is in the bottom.
If you have a small boat, could take a rope with weight marked in foot increments, drop it to the bottom while making a chart of depths. Also in the same operation, if you have a rod of some sort you could push the rod into the bottom of the pond to determine the depth of the muck buildup.
For example, if it were my pond and it were ten or fifteen feet deep in the deepest part, had only a foot or two of muck, that would be an entirely different situation as far as cleanout than if the deepest part of the pond is now only six feet deep. So a depth chart and also a chart of the depth of the muck would be useful information for your final determination.
Cleaning a pond out will be a major investment, but on the other hand it will make the pond useful for a lot more years.
A fish survey would also be helpful. Trapping and catching would be one method. Electro-fishing is another that I have no experience whatsoever with.
