Timely Hatchers

[Tempestuousfury]

I need a clutch of eggs that are guaranteed to hatch within a 3-5 day window (with accurate timing on peat moss transfers, etc.).  I am told that there is a great deal of variability between species and that generally speaking, it's not possible to accurately time when the killifish hatch.
 
I was wondering if anyone here might know of a species that would be somewhat reliable.  I can extend that window to about a week, but the main thing is that I wanted to use the killifish as a model for cell division and general microscopy for some students.
 
Thanks in advance for help with this, and if you have any ideas for other fish that might fit the bill, I am not particularly picky in this regard.  I simply need to be able to ship eggs without losing viability...