There is a lack of standardized acclimation procedures for evaluating treatability of different wastewaters, and such tests are often conducted using different types of microbial electrolysis cells (MECs). Two different types of MECs (mini or cube) were therefore acclimated using two different substrates (acetate or domestic wastewater) to see the impact of these procedures on the resulting treatment efficiency using the same cellulose fermentation effluent. COD removal was slightly larger using mini MECs (81-86%) than cube MECs (79-82%). Pre-acclimation of mini MECs to domestic wastewater increased COD removal slightly compared to non-acclimated tests with fermentation effluent, but acclimation differences for the cube MECs were not statistically significant. Gas production was not significantly different for cube pre-acclimated MECs compared to those acclimated only to the fermentation effluent. Current densities were higher for the cube reactors than the mini MECs, but they were unaffected by acclimation procedure (pre-acclimation or direct use of fermentation effluent). These results show that mini MECs acclimated to a readily available complex source of organic matter (domestic wastewater) can produce equivalent or slightly superior results for tests with a different complex wastewater (fermentation effluent), and that mini MEC performance is comparable to that of cube MECs. The similarity of reactor performance allows the use of simple and inexpensive mini MECs that can be acclimated to domestic wastewater and subsequently used to test different types of industrial effluents.