Hi, I have just picked up a 3foot tank from a lovely free cycler, but I am now wondering what to do to clean it. It is covered in limescale, as we have hard water here, and I am not sure what to use to clean it off. I don't want to use any harsh chemicals which might harm my new axies. Also, if the tank had been used for fish, is there a possibility that there could be anything left in it that could harm them? I know I'm probably being neurotic, but I have spent so long researching as I don't want to harm them. Thanks!