I honestly dont know how to tell if they are ready to hatch. All I know was what I have . In one paper I read said they will become more round and more transparent as time goes on and they get closer to hatching. Mine are all really purple also. I dont think that color means that they arent viable. It can take up to 6 weeks to hatch so I can have one hatched out for weeks while the others just start hatching. There are to many variables to determine which will be viable and which wont.
I just hope more hatch soon. From everything I have read they do better in groups and I am concerned about my one little hatchling being alone and wonder if the other cuttle would have done better if it hadnt been alone.
I am also worried about the other cuttlefish they ordered. I dont think they will be able to care for the properly at the store. They shouldnt have ordered them for you with out having you pay for them first... they dont normally and the fact that they did really ticks me off. Dany assumed that I would take them if you didnt buy them and I would take them but I dont have any more money right now... I really wish I had the money and space for more cuttles but the fact is I wont have room for the ones I have if they all live. Maybe if my husband got on the ball and built my 75 gallon stand AND was willing to just move the 55 gallon to the window like we had planned instead of building another stand to put in the window box I could keep more, but hes not a fast mover on these kinds of thing so I dont think that will happen any time soon.