Metamucil is a psyllium husk product. You can look up psyllium husk and find dozens of products. I believe sand clear is one of them. I get mine bulk at our local grain elevator. Yes, psyllium can cause them problems, but only when they don't have free access to LOTS of water when you give it to them. Once a month we give our horses a cup a head, for 5 days. You can check and see if it's working by taking a few clumps of manure and putting it in a bucket of water. After the manure is dissolved, and removed, you will see sand in the bottom of the bucket.
Sand colic is a big problem around here where it's all sand dunes & clay.
Ask Often, Demand Nothing, and Reward Generously.