I disagree with first reply.
Geos' instinctively feed off bottom. They're called sand sifters, because that is their feeding method.
Their mouths, and the front of their face is sloped for it. They don't really look up for food. more likely to see food if it happens to be at the level they are swimming at....sometimes the lower half of tank, while it is sinking.
Going up to the top is brief, so getting top food is more by chance, not seeking it.
I feed NLS pellets. They like the TheraA most.
I get a pinch of it and submerge my fingers under top water, swishing it between fingers to wet it, and that makes it sink. otherwise it'd get sucked out my top skimmer before they can eat..
A purely floating pellet will have to get all soggy before it sinks, then they don't like it. That pollutes the water too.