I live in Europe and we have different kind of tank sizes. Most likely I will be able to find two 1600 liter tanks which is 422 gallon. My father in law is going to build them but he doesn't speak English, so I will be doing most of the research. I was wondering what the best calculator is online to use? Once we start the build I will start a new thread and keep everyone posted for who is interested in seeing the progress. I appreciate all feedback!