I am planning a build. I have a small room/closet near where my tank will be. I am planning a custom sump and mixing station that fit this space. My question is can I put an overflow on the sump, which leads to a drain and in the same chamber as my ATO, such that I can add fresh saltwater to my display and have excess saltwater flow out of the sump into the overflow leading to the drain to make a simple water change solution? I can't see anything wrong with this idea but I have been able to find any examples of this and was wondering if there was a good reason for this I had not considered.