Silica in the sand mixes with hair and moisture and--well, you found out what it makes. Best solution is to find a way to keep the sand off the hair--a tail bag with elastic at the top might work, or the three-tube type, or you may have to resort to vetwrap or sealtex. Regardless, a week is the max to go between take-downs, and I found when I moved to FL that I had to do it every third day to avoid damage.

Happily the thin white tail is retired from showing, and the new guy has a long thick naturally brown tail that thrives on neglect.