Is it safe? I recently boiled/sterilized a bunch and put some in my 72G, no problems as far as ive seen, but i just want t double check, will i have any problems with it?
If your pH is low they may dissolve a bit but will stop once the pH reaches mid 7's or so. So it may alter thinbgs a bit, but it will do so very slowly. I wouldn't worry.
if your pH and hardness are natually high, they shouldnt do much and may acctually be good for the tank because they will provide places for shell dwelling fish and fry to hide out.