What should be avoided to prevent overcrowding in coral nursery structures?

Preventing overcrowding in coral nursery structures is crucial for the health and growth of corals. A high density of corals can lead to several negative outcomes. Specifically, when corals are planted too closely together, they can compete for limited resources such as light, nutrients, and space. This competition can inhibit their growth and even lead to increased stress, making them more vulnerable to diseases and other environmental factors. High density can also create a risk of physical damage as corals may bump against each other, leading to injuries.

In contrast, other factors mentioned do not lead to overcrowding. For instance, having too many different species might introduce biodiversity, which can actually benefit the nursery environment, while excessive spacing and low-density layouts can promote better growth conditions for individual corals. Therefore, managing coral density effectively is essential for a successful coral nursery and the overall restoration efforts.