In the first few days this is very recommendable, since the eggs have to get a slip and light is necessary for this. If there is enough sunlight on the pool, it is also possible to do without lighting. However, you have to make sure that the water does not heat up too much by the sun. If the room, in which the rearing pool is however rather dark, is an extra lighting needed.
For this purpose, e.g. Also simply use a desk lamp.