z

6.   Fish are scratching on rocks and twitching fins.

 

How does a fish scratch an itch?  They rub against the gravel, rocks, or corals.  This is called flashing because as they turn on their sides to get the itch the paler under belly of the fish is shown appearing to "flash".  They also twitch their fins by rapidly opening and closing them.  Fish will occasionally flash or twitch for no reason.  Everybody gets an itch and fish are no exception.
 

If your fish are flashing or twitching often there is definitely a problem.  Check your water quality especially PH and Ammonia.  Inspect the fish for any signs of parasites or fungus.  If your water checks out and there are no visible parasites you most likely are seeing the beginning stages of a bacterial infection.  This is bad news.  Bacterial infections can come in many forms being external or systemic.  Some bacterial infections show no outward signs or symptoms other than a listless fish.  There are many broad range antibiotic medications available but it's very important that you know which form of bacterium you're treating.  For instance, penicillin might cure one infection but fail on others. 

If you suspect a bacterial infection, as always clean the tank.  Get the water quality to near perfect conditions, note the symptoms, and then consult your local fish store for proper medications.