You don't need a light on them unless you are trying to get the babies to gather in one section so you can sython/ suck them out with an eye dropper or turkey baster.
The filter paper might have something on it that is killing the shrimp, or the container you are pouring the water into.
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When I was hatching brineshrimp, I use a 2 litre plastic drink container that was half full of sea water. I had an airstone bubbling away in it and the container was sitting on top of an aquarium to keep it warm.
After the brown eggs had hatched, I could see easily see the orange nauplii (baby shrimp).
I would lift the air stone out and put the container near a light source (torch). After a couple of minutes the nauplii will be swarming near the light and I used an eye dropper to suck them out in some of the water. I then dripped the nauplii and water into the fry rearing tanks. The small amount of salt won't affect any fish fry.
When I had finished feeding the baby fish, I put the air stone back in the container and removed the light. The container was not in darkness, it just had normal room light.
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You need to start a new hatchery every 1-2 days to have a constant supply of newly hatched brineshrimp for the baby fish.
If the nauplii start turning pink, they have used up their yolk sac and need to be fed. However, you need to move the nauplii into a clean container of sea water because the egg shells start to rot and cause ammonia problems that kill the nauplii.