First Sick Fish

[gjw9]

I have a female swordtail who doesn't seem able to lift the back of her body. She is swimming around with her tail fin dragging. Anyone have any idea what is going on.

 

[krap101]

we need more description. are there any strange markings. and is it swimming lop sided

 

[gjw9]

No spots, not lopsided, just dragging her hind quarters, struggling to swim to top of tank now and then.

 

[Menagerie]

Try looking through these sites:
http://www.aquatronicsonline.com/hobbyist/hobbyist3.htm
http://www.aqualink.com/disease/sdisease.html#ich
http://fish.mongabay.com/diseases.htm
http://www.wetwebmedia.com/AqBizSubWebIndex/fishdisho.htm
http://www.fishpondinfo.com/health.htm

Did this come on suddenly?
Have you added any new fish lately? New substrate? New filter, heater...?