Block desing with several datapoints

I'm a PhD students and confronted with the following problem, hoping someone can give me an advise.
For my research I had to use a more complex experimental design and now would like to know how this can be visualized in an appropriate way for a publication.
I'm analyzing the effect of a treatment and therefore compare a control group with a treatment group. Due to the method I'm only able to gather about 10 data points per day, but I need about 30. When I repeat the analysis on the next day, however, this leads to a strong increase in variation, because the absolute values of both the control and the treatment group are inconsistent between two days. The relative differences however are consistent.
Statistically I encountered the problem using different days as a block, but is there a simple method to visualize the data? When I use ordinary bars, the standard deviation is even higher then the bars. Is it allowed to use the adjusted standard deviation after considering the blocks and how can I find this out. I used Minitab and SPSS for the statistical treatment.
Thanks in advance!!