Not sure what you mean by "pure". Usually this means low heterozygocity and that certainly is not the goal. You want to avoid inbreed depression and the best way to do that is through outbreeding. I don't know the literature on cuttlefish genetic load, but my guess is that it is at least moderate.
So, try to avoid the breading of any hatching from the same cluster of eggs and try to get eggs from mixed sources to avoid any issue? Now that I think of it, pure was a poor choice of wording, genetically sound and fertile is what I was trying to say.
From what I have read on here and another site: Cuttlefish inbreeding is not problematic untill a couple of generations. This may or may not be accurate but even if it is you would have to consider your source of cuttlefish and whether or not they were captive bred/allready inbred. Thales would be a great person to comment on this.
In my opinion however, if you recieve a clutch of eggs with many viable cuttlefish you probably won't have a problem with the next generation. From what I've read, it seems much more a function of food choice that helps deteremine egg viability.
In the future if I have good luck with this batch I plan on feeding high fat diets while mating/egg laying. Also live food seems to help. This may be because they are wild caught and have the correct fatty acid profiles.
If you are really concerned about it I may trade a male with you via cross shipping.