I have had corydoras for a while now but gravel keeps exposing because corydoras won't stop pushing sand or digging. I have more sand than gravel and in fact I removed about 2 pounds of gravel but still have some left. How can I get rid of gravel quicker? It's a pain putting my hand in the tank pinching out the gravel rocks for days upon days. I take breaks due to the fact my feet can get tired just bending down while standing. Thus making me rest but corydoras go and lay on them while I'm gone. What do I do in this situtation?