Linkia stars and starfish in general are some of the most sensitive animals that we as aquarists try to keep in our tanks. unfortunately the stars of the genus linkia CANNOT be target fed, and ARE NOT filter feeders. The "reef-safe" stars (linkia, fromia, etc) that are commonly sold in the reef hobby are constant feeders of micro algae and bacterial slimes. In my personal opinion a hobbiest shouldnt put one of these stars into their reef tank unless it is at least a year old and larger than 55 gallons. A single specimen will quickly consume all available populations of microalgeas, and bacterial slimes in an immature or small aquarium. However, this is not the hard part!
The hard part with these types of stars is getting one that has not been mishandled! These stars are EXTREMELY sensitive to many different factors.
1. You should NEVER touch the stars. The oils that we have on our skin can actually damage the tissue of the starfish. Think of how many hands the star had to go through to get into your tank. Did the collectors touch it? the wholesalers in LA? Your LFS employees when bagging? You whenplacing it into the aquarium?
2. You should NEVER lift a Linkia/Fromia/etc star out of the water into the air. By plucking these animals out of the water, they can get tiny air bubbles trapped in their water vascular system (which allows them to move, i.e. expanding tube feets, etc). The stars have no way of ridding themselves of these bubbles and will often die or slough limbs because of said bubble infestation. Again think of how many hands the star went through. Did the collectors, wholesalers, lfs employees, you take the star out of the water? HOWEVER if a star is healthy and acclimated properly, you will often see it hanging out at the top of your aquarium under the trim, possibly with an arm at or out of the water level. If THEY move themselves out of the water it is OK, they can regulate and compensate their water vascular system to accomodate where they are going(otherwise they would all die during low tide) DONT FREAK OUT!
3. These animals are often parisitized by numerous worms, bacterial infections, other organisms that seem to affect them only mildly in the wild but have a lethal effect to them in captivity, many times only presenting themselves after months in holding tanks, aquaria, etc. If you absolutely must have a star of the linkia/fromia species, or any star in general, make sure that the star is uniform in color/pattern, has no open lesions, is not expelling its stomach/other organs during non feeding activities, and appears active. You do not want to purchase a star that has irregularities in tissue or that looks otherwise abnormal (with the exception of oddly number or sized legs, this can be a sign that the star dropped an arm in the wild or regrew body/arms from a leg).
4. Finally if you do decide on a healthy appearing individual, take plenty of time to acclimate it to your aquarium. Again these animals are EXTREMELY sensitive to rapid changes in water chemistry, and therefore should be acclimated for a period of 3-4 hours, all while following the above guidelines. (dont expose it to air, touch it, etc). If you absolutely have to handle your star, use a rubber glove, or do what i do at the shop and put a fishbag or ziploc bag over your hand!
Finally, even after following all the guidelines above, it still will not guarantee that your star will survive. Most unhealthy stars available in the trade will perish after about 4 weeks in captivity. This is if any of the above were not met. If you have a star that lasts longer than 4 weeks, you should be in the clear. If you are fortunate to get a healthy specimen, they are amazing animals to witness first hand. We had an orange linkia in our show tank at the shop that actually dropped an arm as a means of reproduction, rather than stress. The dropped arm grew a new body and new arms, and is still alive and kicking in the reef! It is a very cool sight and story to be able to share with customers!
If you are interested in purchasing one of the amazing creatures, do your research. Never purchase a star that has just come in from a shipment, leave it at your LFS for a few weeks and check up on it occasionally. Impulse purchases with these guys often lead to doom. And be sure that your LFS knows about the above criteria for linkia/fromia stars. Say something if the employee starts to reach for the star with bare hands!
Hope this helps, sorry its such a long read!
Cheers~!
jon