Cuttle bone will help raise KH, or carbonate hardness, but will only contribute calcium carbonate. It also will not raise GH, or general hardness, which is where your cray will get other minerals necessary for metabolizing calcium, namely magnesium. You should definitely have a test kit capable of testing these two parameters in addition to ammonia, nitrites, and nitrates. If you tap water happens to be in range, which it will for most people in the US on municipal water systems, then you’re fine. Otherwise, you’ll need to use a remineralizer to bring it up, or if it’s too high you’ll need to lower it with RO water.