Growing instructions;  Cattleya's like bright light but no full sun, they should for the most part be slightly yellow green in color, if they become dark green it can be a sign they are growing in too much shade.  Water well by wetting the roots allowing to drain for a few minutes and then water again, the roots are covered with a white velum which repels water when dry but you will see the roots turn green when you water the second time.  As long as you have good air movement and light you can water often in the growing season.  Use a balanced fertilizer such as 20-20-20 in dilute concentrations on younger plants, for older blooming size Cattleya's alternate with a blossom booster fertilizer.  Most all of the orchid growing media will work for the Cattleya's and they can be grown in clay or plastic pots.  When repotting you can remove any rotted roots, the roots on most Cattleya's only live for one to two years so you should not be concerned to find some in this condition.  When dividing a Cattleya always have at least three pseudobulbs in each division and always use a clean or sterilized cutting tool before cutting.