Keep it barely damp until it hatches, then add more water. I've raised one successfully with minced up fish flake--I also swiped extra eggs from the vivarium because at this time, they were breeding like crazy and not bothering to take care of their tads, but you might not want to do this. I actually had the one I raised in a brome axil, so just misted it daily for rinsing, but in a deli cup, you will need to change the water every couple of days, of course. A small deli cup with holes in the bottom put in a larger one may make water changes easier and quicker, since you can just pull out the smaller cup and put fresh water in the larger one. It shouldn't be too deep, maybe 1/2 inch or so, I think. I'm no expert at tad raising--usually just let the parents do it, but at this point, they probably won't pay attention to the lost egg if you replace it.
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Patty
Pahsimeroi, Idaho
4 D. auratus blue
5 D. galactonotus pumpkin orange splash back
5 D. imitator
6 D. leucomelas
4 D. pumilio Bastimentos
4 D. fantasticus
4 P. terribilis
4 D. reticulatus
4 D. castaneoticus
2 D. azureus
4 P vittatus