Magnetic and elastic properties of three-axial (S=2) ferromagnets with single-ion anisotropy have been discussed. The phase diagram in the plane (single-ion anisotropy, temperature) has been constructed and two tricritical points driven by the magnetoelastic interactions have been found. The dispersion of the magnetoelastic excitations in the low temperature has been considered. The special attention has been given to the systems with single-ion anisotropy constantK≈−8 where the softening of a magnetoelastic mode can be observed.