Jason responded the same as I would have. I would only add that if you're adding granular to shock your pool, this can cause scale to build up quickly. But overall, the cell size and cell power doesn't affect if scale builds up, the water chemistry does. Now, if it shows up and you're having to acid wash weekly, it's probably that the reverse polarity is not working properly.
Lower right corner of the display is a little dot (pixel) that cycles on or off to indicate reverse polarity. Every 4 hrs, it should change the on or off status... or in RockCrawler case, every 2 hrs.
Watch your pH level though. It's an often neglected parameter and the quickest to cause scale build up, especially with new pool constructions.