Starfish are very sensitive to ph and salinity fluctuations and often develop bacterial infections because it. I wouldn't recommend it for a small tank especially a Linckia like Kevin said you need a lot of LR and small tanks are susceptible to drastic swings because of the small volume of water. Also if you decide to get one I would recommend you let it acclimate for a minimum of 4-8 hours before adding it to the tank. JME
I have tried several starfish without success
Good luck