adding shells to freshwater tanks

Question
I recently picked up some sand dollars at the ocean.  Can they go into a
freshwater tank after cleaning?  Should I boil them to make sure they don't carry
any diseases?  Thank you.  

Answer
Hey Carolyn,

No, they cant. Sand Dollars are going to change the hardness and pH of your water, and if there is leftover dead flesh inside the sand dollar, the ammonia resulting of adding these decorative remains will kill your fish. Although pretty, sand dollars are best kept around the tank, not in them.

Sorry, and best wishes!