How old is the aquarium and what does it contain? I couldn't say if I would recommend a "linkia" to your tank without knowing more about your setup, including how old is it, how many pounds of liverock are in the tank, what filtration you're using, water parimeters, and other livestock.
Also, The Linkia guildingi (orange linkia) is not a 'True' Linkia starfish. They are commonly known as the 'Orange Linkia,' (dispite that it's not a true linkia), or the 'False Linkia Starfish.' These starfish are much more hardy to keep in the home aquarium, and prove to be much easier to care for, compared to the Blue or Purple Linkia Starfish (linkia laevigata).
The exact food for the Linkia guildingi is unknown. We can only assume it eats films of algae, some species of sponges (Guessing Pineapple Sponges and encrusting sponges?), bacteria and possibly some species of pods. We can only guess that they do best in mature systems with high amounts of liverock; we can say that because the most success from these starfish comes from tanks which are mature with lots of liverock.
Remember,
All starfish have extremely sensitive hydrovacular systems, which are extremely sensitive to even the slightest change of pH, temperature, and salinity. Therefor, acclamation should exceed 4 hours (most people do 6-14 hours) using the drip method for aclamation. Otherwise, it may cause damage resulting in Loss of limbs, shrinking, and slowely dying (sometimes discribed as "Melting") off. Other methods of aclamation are often too quick and very stressful to the starfish.
Take Care,
Graham