poop

I have noticed quite a few of my fish having long strings of poo that is very thin and white/clear almost like a strand of hair. A quick search indicated worms however when I looked on Google images all the pictures I found the worms were fat and earthworm like. I have enclosed a picture of one...

Is this a poo or a worm/parasite? Seems like an awfully long poo!

1. What is the size of your tank? 55 gallon and 10 gallon 2. What are your water parameters? State the brand of test kit used. Mardel (10 gallon) PH 6.6, Ammonia - 0.00 Around 80 degrees Fahrenheit. <-- My pregnant guppy/fry tank. Seachem (55 gallons) PH 7.8, Ammonia 0.00. Around 72 degrees...