fish bugs

Question
I have a 55 galon freshwater tank with mollies, platies, and some
corydoras, and two gobies.  I was watching my fish the other day, and I
noticed these tiny little bug like critters crawling around on in/on the
gravel.  Then a couple of days later I noticed them all over the place,
even swimming about in the water.  I have no clue what these things are,
or if they are harmful.  They are off-white in color, and really small,
like the size of half the size of a sesame seed, or even smaller.  Can
you by any chance tell me what they are, where they came from, if they
are harmful, and how do I get rid of them.  I have a clean tank, and
it's been up and running for 6 months and this is the first serious
problem I've had.  Thank you so much for any help you can give me!

Answer
Those little bugs are realitively easy to get rid of. I have gotten them in my for no apparent reason as well. I do not know the name of the little bugs but when I had them I cleaned my filter really well, the tank gravel(50% water change) and also scraped the glass and repeated about half week later. Each time adding Aquasafe to lessen the stress on the fish in the tank. Happy fish keeping!!