The pond is lined with plastic so no rocks are found except those placed in the artificial nest. The nest has a window screen bottom within a two-foot square wood frame. One-inch sized rocks are placed in a separate hardware cloth basket, which rests on top of the window screen. Eggs spawned on the rocks hatch in about three to five days, depending on temperature. Newly hatched fry are transparent yellow wigglers that work their way deep into the rock pile.
Rocks provide natural protection while the fry are most vulnerable.
With the artificial nest box the natural wiggling action places the fry under the rocks but on top of the window screen of the nest frame. As the fry grow and develop, they take on a black pigment. They wiggle in the rocks for another three to five days until they develop swimming ability. The proud papa guards the nest heroically during this critical stage of development and wise hatchery managers let him do it. But once fry swim they become very difficult and time consuming to capture.