This is not a quarantine tank it is my 55 gallon guppy tank. My fish are darting off my arm when I clean. They don't dart any other time. Is this an illness or just a greeting? It only started after one of my big mommas gave birth. I am trying to decide if I should treat for illness or not. My water had a small spike in nitrites but had been corrected. I just did a 50% water change and cleaning tonight when I noticed the darting so I will test water tomorrow.