white dots in the aquarium?

Question
Anna:
I have a 10 gal tank thats be running for four months.
It has a dime sized angelfish,
two female guppies and a mystery snail.
lattly I've seen little pen dot sized white specks in my tank,they swim around super fast and seem to have a hard shell.(making them hard to smash.)  what are these things and are they harmful?!

Marissa:
I have a 50 gal. tank thats been running 6 months.
It has two rainbow threadfins,three Discus and a lot of snails.
Today Anna pointed out that there are tiny white worms in my tank that are maybe half a cm long. they are always moving.
 I think they're planaria, but am not 100% sure. Any ideas?

Answer
Hello Anna,

It sounds like your snail had babies., which is not a bad thing. I have snails in my Betta fry tank. You can pick them out if you like or leave them in.

Marissa,

Yes I agree it is most likely Planaria, and not to worry they are harmless. You get them by over feeding your fish, or not doing regular water changes. Some fish do eat them. If you want to get rid of them, cut back on the feeding, meaning feed less, and do a 25% water change every week.

Good Luck to the both of you