When females first lay eggs, they're not very good at it. By the fourth clutch or so, the eggs tend to be closer together and there are usually more of them. In other words, the females actually get better at laying the eggs. The males on the other hand, are responsible for caring for the eggs. And they tend to get better at this as well. They remove eggs that aren't fertilized or have ailments that prevent them from hatching or could spread to other eggs, and tend to keep a closer eye on them. The males fan the eggs to bring them oxygen and also guard them from other tank inhabitants. In my DT, my female Onyx shoos the male back to the nest when he wanders too far. My second clutch dropped to about half the size during the second night -- I attribute this to the male not doing a good job of guarding the eggs. Subsequent clutches have gotten larger and larger.
You can raise the first batch of eggs, but the rationale for waiting is also that since the parents get better at laying and caring for the eggs, the young should have less defects and should be stronger. Also, since the clutches tend to get larger, you'll be able to raise more babies (if you like). I pulled my first set of babies from the parents' sixth clutch. Since the female laid eggs on the overflow, I had to manually remove the babies from the tank, so I only removed a couple dozen or so. I waited a few clutches to raise another batch, and the second time I removed over 50 babies. For percs, you can expect to have a couple hundred babies.
