First time owner-Black water tank clogged....help!

Unique RV Digest-it. It says pour a large bottle of it in there and within 24 hours it will eat the pile. I use it regularly in my black tank. I've had the mound twice when water is not used enough. Water is your friend. It's not fun trying to get rid of the mound and the advice to wear a face mask if using a wand is to be well taken. Good luck. You aren't the first and you won't be the last.