it depends on what you want to do. Once a day or every other day will be adequate to keep them alive. 3 or more times a day is more of a diet you might use to get them spawning. Always feed as much food as they'll take in 5 minutes with as little waste as possible. It is also best to provide a varied diet or flakes and frozen foods. I use all of the following in a random rotation: 2 different home made frozen foods, prime reef flakes, formula 1 flakes, live brine and frozen mysis.
It is important that you skim well and test your water regularly to keep nitrates in check as pooh mentioned.