I was called to look at a pond the other day. This is my first experience with any water features. So any help would be great. The pond in question is in the area of 2500 gallons or so. There are more then 50 fish in this little pond. The owner has done little or nothing to this pond. Other then add too many fish and to many plants. Just my thoughts there. They have tried several filters with no results. It is filled by well water or rain water. Just a rubber liner. Pic one is of the pond from a distance.