Hello, I have just a few quick questions regarding the buffer filter and the settings for the water circulator during the ETC step. First of all, how often do you replace the filter cartridges? I am in the process of assembling my apparatus and I'm not sure how many replacement cartridges to order. Secondly, what level do you have your pump flow/pressure at during ETC? Do you change out your clearing solution at any point during ETC? Finally, did/does your circulator have any problems with circulating the clearing solution? Thanks so much for your help.