I've had a 20g aquarium for over a year. It was well established. However, I had to move. During the move, something made my tank crack and start spilling water. I quickly bought a 10 gallon and filled it with the gravel, water, and filter media from the established 20 gallon. I will get another 20 when I can afford it. I have 4 peppered cories, 4 rummynose, and 5 neon tetras. I know this is overstocked, but it's the best I can do for now. I tested the water before and all was fine. But today, the test said I had high ammonia, no nitrites and no nitrate! What do I do? The lfs's around here are nasty Terrible and the fish would be worse off than they are now. And the rummy nose still have red noses. How can I fix this without killing the fish?