little worms

Question
Hi Chris,
I was wondering if you could help me out with the most disgusting thing I have ever found in my fish tank!  I was just doing my regular cleaning of the filter and when I took off the cover, I noticed that there were little black things all over the white filter bag.  I first thought that somehow the charcoal had leaked out, but then upon closer inspection I noticed that they were moving and that they were worms!!!!!!  They are black and about 1/4 to 1/2 inch long.  I haven't added any new fish to the tank for about 6 months.  The only new addition was a live plant that I put in probably about 3 months ago.  I have noticed however that the tank seems a little less clear, not as crystal clear as my other tank that is next to it.  The fish seem to be behaving normally and there is nothing visible on their bodies.
So the question is---what are the worms and how did they get there?  Also, are they going to harm my fish?
Please note:  I am a high school biology teacher, so I can understand the technical end of things (if you will).
Thank you so much! I can't wait to hear your response.
Thanks!!!!!!!!!
Rebekah

Answer
Hi Rebekah;

Welcome to AllExperts!

If the water is cloudy and you have little creatures in the filter eating the waste, these are both signs that you are overfeeding. We all overfeed from time to time, but we have to be prepared to clean up after ourselves when we do.

Make some 25% water changes over the next couple of weeks while vacuuming the gravel. Do the changes maybe twice a week until the waste matter is reduced. Feed less food and make sure the fish eat all of the food from everywhere in the tank within 5 minutes. Once per day is fine.

The worms are simply something like you might find in a pond or anywhere else that things grow in water. They might even be baby tubifex worms that came in on the plant roots and the fish have been eating them before you even see them. Tubifex worms are fish food, so they would love them! If whatever they are were harmful to your fish you would see a problem by now.

Followups welcome.

At Your Service;
Chris Robbins