if you have gravels then yes. if you have sand then no.
sometimes harmless sometimes harmful.
having gravel gives parasites and potential harmful worms a place to side.
most likely due to left over food that gets under the gravel uneaten then forms worms.

[/B]your saying that leftover food forms worms?![]()
I have never had any worms in my tanks, other than blackworms. lol I put them there on purpose though.
