It seems most people just keep a couple of sepia bandensis together. There are articles stating you can keep them in larger groups in larger tanks and others mentioning fighting. I thought I'd share my experience and get other peoples comments. In case you don't know my cuttle tank is a custom 90 gallon its 36x24x24. Lots of live rock, lots of hiding spaces, I even put a breeder net full of cheato in to give them an additional option + I'm hoping eggs will be layed in there. I started with about 12-13 in the tank now I'd say I'm down to about 5-6. It is not a water quality or food quantity issue. They are fed daily and the tank has a very powerful skimmer and corals are doing well. I have seen the rings on cuttlefish that i learned on here are a result of fighting. One who has since died also had a very puffy eye. I have seen lots of mating an courting but no eggs yet. I am assuming most of the fighting is a result of mating, but I can't say for certain. This is my experience with a larger group thus far. I'd love to hear others.