Nematodes

[Backfromthedead]

They are in your filter.
Next time you do a water change take your bio media and vigorously swish it in some of the water removed from the aquarium and rinse out the filter housing also throw out any mechanical media and replace it.

vigorously!

im sorry that made me lol

 

[jaws7777]

Do as tlindsey stated and also starve your fish for a week or so maybe more ive had them in the past im sure we all have them but dont notice them until the poplulation explodes. What type of fish are you keeping ?