white worms in tank

[Err]

Roundworms are red. His are white. Therefore planaria. Maybe you should do some research... And they (roundworms) wouldn't come in on prepared or frozen foods because those foods are processed and/or frozen.

And some planaria are brown,black,red depending on what they are eating as well as some roundworms are white/brown/black. Unless you throw the little bugger under magnifacation and get PID on it, it could be a number of things.

http://nematode.unl.edu/key/nemakey.htm

 

[GMFISHNUT]

If they are stuck to the glass, they are probably planaria. They are harmless to your fish but can be unsightly in the tank. Feed less and when changing water vaccum the gravel to get any uneaten foods out of the tank. The only way to control them is by not overfeeding.