Where I live, it's currently 12:40, and I couldn't fall asleep so I went to look at my fish tank. I have a 20 gallon tank with 5 guppies and I'm using tetra safe start to help cycle the tank. Earlier today, when I tested my water, my ammonia was about . 5-1 and everything else was 0. My ph is about 7.6 and the water temp is 80. Anyway, I turned on my lights, to look in the tank, and when I did I saw one of my fish not moving, then he sank to the bottom of the tank. He stayed there for 3 minutes. I thought he was dead. He then started moving a little, and went down again. A few other fish did the same, but not for as long. Is this normal? Do fish rest a little at night? I'm so worried.