Hi, I recently purchased a 125 gallon tank from friend. I set it up in the house about 2 days after I got it. The tank came with coral substrate that was kept in his tank before I bought t it. He drained the tank the day I got it. I kept the the substrate in plastic trash bags until I added it to the conditioned (prime) water I had added to the new tank (substrate was in the bags about 2 days). I also had hooked up a sun sun 303b cannister filter to my existing tank about 9 days before I hooked it up to the new tank. Now I've been doing a fishless cycle for 8 days now. I've added ammonia 3x during this week.. Now I'm having the ammonia reading drop from 4ppm to 0.25ppm overnight but no nitrites and nitrates sitting at about 5ppm. I've gotten this reading for 3 days now. I'm guessing I'm cycled now. But I'd like someone else's opinion.