I have been long overdue on cleaning my saltwater mixing tank. I use (2) 65g poly tanks for to hold the RO and Saltwater. The SW tank needs be cleaned yearly because I use Instant Ocean salt and it leaves plenty of build up on the walls. I finally took the mixing system down this past weekend, filled the SW tank with a citric acid solution, and added a couple of strong powerheads that were directed along the wall to create a circular water flow. Before I added the solution I tried removing the build up with a brush with no success. After the solution was left to flow for a couple of hours, the inside of the tank was completely clean and did not require any additional attention. On a separate note, when I reset up the saltwater mixing station that is automated by Hydros controllers, everything came back up perfectly.