small white thing?

Question
I have a fairly large tank, probably 50-60 gallons and it has had no problems whatsoever.  However, I cleaned the tank yesterday after having let it go for too long without a good water change.  After getting everything put back in, I noticed a small white thing swimming toward the surface.  The tail looked like a worm, but it did have legs from the front to the middle of the body.  And it had visible eyes.  It was maybe an inch long.  It reminded me of a mini scorpion like creature.  It was gone before I could catch it or photo it, and I haven't seen it again.  My fish seem ok, but I am worried this may be something bad for the tank.  I have reproducing guppies and don't want them all to die - help please!  I hope this is harmless and I am overreacting...

Answer
Hi Deanna,
I don't think the little 'scorpion-like creature' is something you should worry about, unless you see many of them, or unless they are attaching to your fish. Without a picture, it's impossible to tell, but it sounds like a crustacean, not a worm or parasite. Some crustaceans are parasitic, but many are not, as well. Perhaps you bought some shrimp, and they reproduced? Anyways, many undesirable organisms thrive in dirty water, so be sure to do 10-20% water changes a week. Just keep an eye on the guppies to make sure that they are well.

Sorry for the slow response; I found this in the 'answer pool' of unanswered questions.

I hope all is well with your aquarium!