Hello, my girls won 6 goldfish at the fair..... I had a 10g tank. Five died, we thought the other was lonely, so we bought lots of fish. They started dying, so I started researching what could be wrong. I now know about cycling a tank. Too late for all the fish, though. After researching, I purchased everything I needed and began cycling the tank. I bought a heater and cleaned the gravel with the little vacuum the best l could. There was still some food left in the rocks, though. It's probably been 7 weeks that the tank has been set up and running. Four days ago, I added the ammonia and the test shows the 4ppm is back to 0 the next day. I tested for nitrites but it was, also, 0. Well, today I decided to check for nitrates and it showed 80 ppm. I missed the nitrites somewhere!! I don't understand the instructions that stated the cycle would be 4 ppm one day and 0 ammonia, 0 nitrites, 0 nitrates in 24 hrs. But then it says that the only way to reduce the nitrates is by PWC. Has my tank completely cycled?? If so, I know I have to do a 90% water change, turn the heat down and keep the bacteria fed before I purchase fish. Another question is, what type of cycling would I have to do to a new tank since I want to purchase a 20g long instead of the 10g I am now cycling??? Thanks in advance for any advise I may get!!