Well... This is how things went, I turned off everything, siphoned some water from the tank into a 5 gallon bucket, that I use only for the aquarium, to clean the pump's sponge, the sump's sponge, and the filter pad with aquarium water. After I finished cleaning that, I drained 80-90% of the water with a Python and then, poured dechlorinator to the 10 or 20% water left in the tank. I use Tetra brand dechlorinator, it says it removes chlorine, chloramines, and ammonia, measurement is one teaspoon every 10 gallons, my tank is 120 gal. so, I added about 13 or 14 teaspons, a few more than I had to, which I suppose it doesn't hurt. Finally, I started filling up the tank again with water and when I was almost done filling it... another unpleasant experience in this hobby, but it only makes me love the hobby more and more (although it very frustrating and discouraging at moments, but it was my own fault). What happened was that when I was almost done filling the tank, since I have internal overflows I don't know why, probably because I was tired, I didn't realize, it didn't look like it, but the water was already going from the overflows to the sump and, yes, guess what? Flood!!! My sump was full of water, so I removed the Python, removed some excess water from the sump and had to dry half of my living room (no carpet), I also had to remove everything from the cabinet, except the sump, dry it all out, dry the floor, move some furniture, dry the cabinet, my GF complaining. As I was cleaning, I started the pump, air stone and heater and after I was done doing all that I siphoned the remaining excess water from the sump and left it at the proper level, then it was time for testing and these were the readings (about an hour or two after the tank was filled with new water) Ammonia: 0.25 ppm, Nitrites 0.25 ppm, Nitrates 20 ppm, nitrates are very difficult to distinguish some colors on the color chart, I think it was 20 ppm but it could be 10 ppm, at times it looked like the color of 40 ppm but it was to orangish to be that color so, it was either 20 ppm 0r 10 ppm, leaning more towards 20 ppm. After testing I've added one tablespoon and one teaspoon of ammonia because it's been about 30 hours since the last time I added ammonia, and I obviously need to feed the bacteria while I don't have fish. Now, I will stop writting for a second and test for ammonia and nitrites before I go to bed and see where they stand right now, it's been about 35 mins. since I added ammonia. Okya, these are the readings: Ammonia about 3 ppm (did I add to much?), Nitrites 0.50 ppm. Are this readings logical? What about the ones I got before adding the ammonia? To my understanding, if the tank is cycled it should drop to 0 ammonia and 0 nitrites in about 10 hours from now, right? What about nitrates, are those going to be high tomorrow because I added ammonia a few minutes ago and it will do the nitrogen cycle and end up as more nitrates or it takes a while to build up? Should I do a 30% water change if nitrates are still at 20 ppm tomorrow? I really want my nitrates below 10 ppm. I just want to stay on the right track. Thanks!