There are several schools of thought on this issue...I have no idea which one is right. I tend to lean towards the fact that everything needs to rest. You have to remember that the same cooler temperature which is delaying your hatch, is also slowing the metabolism of the embryos, causing them to in turn use less of their yolk sac per day. I have no idea where the balance between these two is, but I can tell you what I do, and my clarks take 10 days to hatch also.
I do feed them rotifers (water clouded with phyto) directly after hatching. I give them about 3 hours to practice hunting and eating, and then it's lights out (usually around midnight). They get 7 hours of sleep before the lights kick on at 7:00, at that time, i re-cloud the water with phyto, add more rotifers (probably to a higher density than is prescribed in what I've read). From there they are on a 16 on 8 off light cycle through the duration.
I'm no expert, but I do have 200+ 3 day olds with maybe 20 losses so far. They are all fat, happy, and energetic. The first three days are a trying time for them, in my first few hatches, I would often loose all of them on night one or two. I believe stepping up parental nutrition is what fixed this problem.
On Day 5-6 I switch them to newly hatched artemia for 2-3 days, and then wean them to powdered dry foods (Otohime this time, was using Formula 1 and Cyclopeeze). Once they get through metamorphasis and into dry foods, it's all up to you, and you tank maintenance. If I relax in this area for a day or two, a few deaths are sure to follow.
Good luck with them, many breeders do leave the lights on, maybe they can detail their method too. I don't claim to be "right", but I have had some success, and will gladly share what I've learned.
Jason
