Joe, My pair spawned about 20 times before it dawned on me that my water was too hard. My water was 175ppm Total Dissolved Solids. I purchased a RO unit and brought the ppm down to about 25. They raised the next spawn. A screen is OK but do you know that it's almost impossible to raise Discus fry without the parents doing most of the work & feeding? The fry pick their food off the sides of both parents. I do know that some people have raised fry without the parents but it is very difficult and time consuming. If you have never raised fry by yourself before, I would say this would be quite a task to undertake. As always though, I wish you the best of luck in your endeavor. As for hatch time, if the water is warm as it should be, at least 82F, the eggs should begin to wiggle in about 4 days and then another 4 before free swimming.