Do you NEED to give it to them? That's up to you, but it's a heck of a lot cheaper than trying to resolve an impaction colic.
As far as paying more for Sand Clear when there are products much less expensive that are the EXACT SAME THING, again, that's up to you. I don't feel a need to throw away money like that.
Most people are thankful when others tell them about things that cost less, not get snotty.