Charcoal biscuits?

[kim]

I've just brought a selection of dog biscuits from pets at home which includes some charcoal biscuits and I just wanted to know if these are safe to give to the gerbils. I know they can have meat, cheese and vegetable dog biscuits/treats but I've never heard anything with regards to charcoal ones so just wanted to check before I feed it to my boys. 

Thanks