Bowl feeding is a very good way to feed fish any sinking food. It is cleaner, allows you to monitor which fish are eating and how much, as well as if the fish are being over or under fed.
Many fish are hard to switch from one food to another. Feeding them in a bowl will get them to associate the bowl (and you putting things in it) with food. This makes it much easier to switch them to the foods you want them to eat, not just what they choose to eat. This can help switch many fish over to prepared foods and off of risky, less nutritious live foods. This works for knife fish, spiny eels, freshwater rays, and many others.
Most fish will quickly learn any patterns that are related to food and being fed. Using a bowl provides them with a specific spot they know food will be, rather than it being all over the surface (which can lead to some of the food ending up out of sight behind filters, tubes, and wires), all over the bottom, or trapped in and under plants and other decorations. All of these circumstances can lead to uneaten, rotting food that will lower water quality.
Bowl feeding also allows the aquarist to monitor which fish are eating, and how much they are eating. This can have huge advantages in making sure all fish are eating, and spotting any problems with dominate or subordinate individuals. Aggressive behavior is usually amplified at feeding time, even though in general it seems they all get along. Having all the food in one spot will allow you to see if any of the fish are causing problems for other fish, or are being harassed too much. With food all over the tank it is hard to catch problem fish in action. I find that many of the fish feed in shifts. Certain species or individuals will be the first to feed. As they fill up and go about their business others will move in for their turn. Because of this, feeding guides like ‘no more than two minutes’, ‘3-5 minutes of feeding’, and others are not always the best to go by. By allowing more time for feeding you can ensure that all the fish get a full meal.
I use an under gravel filter riser tube (three feet long, one inch in diameter clear plastic) with a funnel taped to the end to put the food in the bowl. The tube sits in the bowl while all the food sinks, then I remove the tube, which releases all the food into the bowl. By this time most of the fish know it is feeding time and are waiting for the food to be released. I use a measuring spoon to put the food in the funnel. This also allows me to keep track of exactly how much I am adding and easily make adjustments, rather than just grabbing a pinch or two.
All of my tanks are only fed one food (New Life Spectrum), so all the fish feed out of the bowl if there is a bowl in that tank. All the fish learned very quickly that the food was in the bowl. My tiretrack eel was always the first one to the bowl. While the food was still in the tube sinking, he would literally put his snout between the bowl and the tube and tap the tube up, releasing some food that he would quickly suck up. Cichlids will learn where the food is very quickly too. Even less intelligent species such as Characins will learn very quickly that the food is in the bowl.
The bowls I use are heavy reptile feeding bowls. They have a natural look to them, making them fit in more with the decorations in most tanks. They are relatively cheap and very durable.
Bowls are especially useful when feeding sinking foods on a substrate large enough to let the food fall between the pieces of gravel and out of reach to the fish. The bowl keeps the food on top where the fish can get to it.
I have even used this method to get freshwater stingrays to accept pellets within one week of arrival in the store. I started them on black worms just to make sure they were eating in general, then quickly moved them on to pellets.