Sinking feeders have specialized mouths that are pointy and can snatch food as it sinks from the top. Bottom feeders have specialized mouths that are shaped to suck or pick food as it settles on the bottom of the tank. Some fish can feed at two or even three of the levels. It is important that you know what type your fish is so that you can be sure to buy the appropriate type of food. In general, flake food is for floaters and sinkers because it floats for awhile and then sinks slowly.
Tablets are for bottom feeders because it sinks quickly to the bottom, bypassing the two top levels.
Pellets are for floater feeders and bottom feeders because some of it floats while some sinks directly to the bottom. Freeze dried food is very convenient because of its shelf-life. Live foods benefit the meat eaters who have a need to hunt and are looking for movement. This bacteria seems to crop up most when there is the smallest of direct sunlight hitting the tank and may be affected by a drop in the nitrate levels. All other filter types just trap the waste and wait for you to clean out the filter.