Having two tanks gives you two specific advantages: 1. The ability to clean two different types of parts. This is especially important with bio-compatible resins that cannot be cleaned in the same tank as parts printed with a non bio-compatible resin. It also needed to separate class I and class II resin that cannot be washed on the same tank . 2. The ability have a two-stage cleaning process, i.e. a deep clean and light clean. Using separate tanks like this can save 50% of alcohol because you can cycle the tanks so that only one is ever close to being excessively contaminated.