Blue Linkia's are specialized eaters. To the best of my knowledge there are no prepared foods for them. They eat algae slime or some thing like that. You want to have a tank that is pretty well established.
Also keep in mind you don't want to touch them with your bare hands, as it can cause them to die. Also when you transfer them from acclimation to tank you want to keep them in water, don't let the air hit them. I used the plastic bag they sent him home in to take him out of the bucket. The other thing to keep in mind with them is, they require stable water conditions. Low nitrates and stable PH and SG.