The loading of eggs into Heath incubator trays is dependent on existing conditions
and the facilities available. Brown and Gratzek (1980) reported that rainbow trout fry
have hatched successfully in units with 45000 eggs per tray. The acrylic ring was
attached to the bottom of the Heath incubator trays to confine the eggs and to simulate
densities of eggs at a typical hatchery. However, the density of eggs loaded at a hatchery
is approximately five times greater than the egg density used in our study. The lower
egg loading used in the chemical efficacy tests may have affected the occurrence of
fungus on all treatment groups.