Mare has sandy gut

My mare has sand in her gut. We live in the south so this pretty typical but it's bothering her bowels. We did a treatment of Equisand on her and her stool is much better but not perfect. Asked the vet what to if anything to do and she recommends putting her on Equisand daily. I know it can't hurt her but the pysllium is expensive and all the instructions on all the products say to use for seven days per month.

What are your thoughts? I am going to call the vet when I get a break from work.

Maybe flax seed or Rice bran.

Flax seed turns to a gel in the stomach and I have heard can help with clearing sand.