Freshwater Aquarium Sand vs Gravel: Which to Choose | Hepper
Gravel is usually large and heavy enough so that fish, air pumps, water pumps, and filters won't be able to stir it up. Simply put, it's too heavy to float around like sand does, and therefore does not result in such a mess or clogged aquarium components, or cloudy water for that matter. The gravel itself is usually quite easy to clean.