I actually have sand in one of the two soils I mix together. It helps with draining. Just not too much sand. I have used it with no adverse effects. Instead of every 5 days, I have to water every four. I have seen people use really soggy and moisture holding soils and have ph problems, mold and fungus because of not having properly draining soil. I don't know how much sand you put in, but I always use a bit in my mix.
Good luck,
Elway