The hairgrass should not be lifting up from the soil exposing its roots, they should be firmly rooted into the soil.
Did you plant the hairgrass in small bunches of a few blades each, or in large bunches? Usually if planted in large bunches, the bunch may become buoyant and without established roots yet, would tend to float up. Its best to separate them into smaller bunches before planting.
Its also possible your corys may be disturbing the plants when sifting around the bottom for food too, have to observe them to see.
Bookmarks