Primarily they need to be on a diet of prepared foods as many just simply don't survive in captivity due to lack of available live foods.
I had good success in a 200 litre tank with the following method of training them to frozen mysid shrimp:
- Acclimatise new mandarin
- Release into a breeders net within the tank.
- Put some macro such as a Caulerpa sp. in with the mandarin to reduce stress.
- Feed 3 times a day - morning, afternoon and evening, more if you are home
- Defrost mysid shrimp in saltwater from the tank and introduce a small amount to the breeders net with some tubifex worms. For the first few days they will mostly eat the tubifex worms but will mistakenly get the odd mysid as well. They then develop a taste for them. Over the next 2 weeks, gradually phase out the tubifex.
Should take 2 to 3 weeks to get them not only trained on prepared foods, but recognising you as the source of it and showing a feeding response when they see you. Once you are certain they are eating well, release into the tank. At feeding time, pumps should be turned off, as the food needs to settle to the bottom of the tank or onto the rocks so they can go around picking it up off of a surface. They occasionally grab food from the water column but if you watch the way they hunt, you will see why the food needs to be on the substrate or rocks.
I found that they occasionally go off the frozen foods and you should act fast if they stop eating it for a few days, otherwise they lose weight quickly. They need to be caught and put in the breeders net for re-training. Pretty high maintenance fish when it comes to feeding.