Hello, I have hatched out 10 Sepia officinalis or elgans two months ago. They are currently 2" mantle length and are about to move into a 100 gallon tank. The question I have is whether or not to provide a substrate on the bottom of the tank and if it is recommended that I do, what form of substrate is best. I have coarse and fine coral sand which I think may be too rough but I can get small rounded gravel or sand. My main concern is damage to the animals and also a crumpled rear end which seems to be apparent in some public displays. Your thoughts are greatly appreciated.