To reduce food sinking too fast and disappearing into the substrate, just feed in small amounts and wait until the fishes finish eating the food, then feed abit more.
Or feed floating food pellets/flakes, those will stay on the water surface for a longer period of time.
Personally i feed my fishes with New Life Spectrum Thera+A Small Fish Formula 0.5mm pellets, but i further crush the pellets into powder size and scatter them on the water surface, the tiny granules stay floating on the water surface for a while until eaten.
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