How can I tell when my copepods have reached a maximum density? I've been culturing Tig and Tisbe's for a year and still struggle with when to harvest. Once per month I remove 50% of the pods and media then top off the media for the remaining pods. My current batch of Tigs are due but don't look as dense as I'd like. I've tested for ammonia in the past and don't get a significant amount.