I have a few questions regarding my new (5 week old), 12 gallon tank. 1) I did my first water change, a 3 gallon, last weekend because my nitrates were at 20 and my ommonia was at .25. After the water change, my nitrates have done nothing but rise to the 80 they are at today, and ammonia is at 0. How do I lower my nitrates and why are they rising? 2) A couple nights ago, I saw 2 small (2cm), blue worms on the glass, about .5 inches out of the water. When I pushed them in, they started wriggling like snakes which caused them to swim around the tank. What are they? 3) When should I place one of those small fish (which type) ino the tank to get it used to a bio load?