I've heard alot of people say that when you turn the light out on the aquarium at night, and shine a light in some time later, you see little copepods and other things. I have done this many times and I do not have anything. Is this something to be worried about? Also, since I can't see them, does this mean more than likely I have none? My last question is that when I did a 10 gal water change today on my 55 gal tank, my nitrates went down to about 20 mg/l and I waited about 2 hours tops and did another nitrate test...and they went up to about 40 where they've been. Any ideas on how this is happening??