I use cuttlebones as well, never had problems with my fish. Some will nibble on them, but I don't think it'll hurt them.

Can you put cuttlebone in my aquarium?

In aquarium the bone can be safely used to saturate Akadama. We know that this type of substratum absorbs carbonates and then lowers the pH of the water. Increasing acidity dissolves our bone by releasing other carbonates. These will be absorbed by Akadama and so on until the saturation is complete.

How do you prepare a cuttlebone for a fish tank?

As the the cuttlebone dissolves in the water it releases calcium that snails need for shell growth. Some place them inside of the filter, while others will boil the cuttlebone to make them sink, some even let it float at the top of the tank. This is easier to use instead of putting liquid calcium in your tank.