I would appreciate some help to find out the correct design matrix for my experiment in EdgeR. The experiment is about thermal acclimation in fish, where I have two groups 1.Control 2.Treatment. From each group I have 2 tanks, so 4 tanks in total, 2 from control and 2 from treatment. I sampled fish tissue from 6 fish from each tank. I am interested in genes which are differentially expressed between the control and treatment. However I have 2 tanks from each group but I am not interested in the difference between the tanks of same group. At the same time I have to take into account the tank effect which I could do with a nested ANOVA. So my question here is Is there any model close to nested ANOVA that fits to my experiment in EdgeR? I looked for different possibility in the manual but most of them are crossed models which does not fit to my experiment. Also I am a newbie here so I might have overlooked on the possibilities. Any help will be greatly appreciated. Thank you in advance.