Once a day feeding is perfectly fine for most fish, although some herbivorous fish like Mollies have smaller digestive systems and can do better on more frequent feedings. It is always good to check when you buy your fish what their recommended feeding pattern is.
Splitting your feeds throughout the day does actually match the natural feeding pattern of most fish better. However, when feeding more often it can be tempting to overfeed which should be avoided. Fish will generally always eat when it is offered, even if they are not particularly hungry. They will also quickly learn who brings the food, and can ‘beg’ in their own way, so don’t be tempted to succumb to the pleas of ‘starving’ fish!
However you choose to feed, routine is best, so try and feed your fish at the same time every day. If you have nocturnal fish, such as some catfish, make sure to consider that when planning your feeding regime.