Pond leeches??

Question
Cleaning filters this morning. opened the big filter and flat worm like that strtched about 2 and 3 inches. off white in color, heads looked like hammer head sort of. they looked like intestine.
Are the leeches of some sort. Will they hurt the gold fish in outside pond. While were at it lots of green sludge on bottom of 4'x10' x 2.5deep. about 800 gal pond. with same 800 filter. have some aquatic plants. water is always murky . I have seen clear ones and thats what I would like. Any ideas, help, or point in the right direction thanks, Pat


Answer
Dear Patricia,

Thank you for your mail.
Without some picture it is not so easy to guess what kind of insect is in your filter.
Maybe, however, it is a rattail maggot like you can find in following link.

http://upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Rattail-maggot.jpg/755p...

If so it means that the water/area is almost without oxygene and so it's maybe necessary to check your filter as anaerobic surfaces could cause diseases.

To answer you question in a broader way, I think it is time to update your filtersystem.
Create more filter area, a prefilter to get rid of the visible debris, and aerate the filter.

Please feel free to contact me again for more information if needed.
Hopefully my answer helps you to enjoy the pond more!