Cichlid aggression

Question
We have an 85 gallon 4 ft tank with 9 yellow labs and 9 yellow tale acei(juvies). The labs are about a year old  and have been in the tank for about 9mts. The 2 largest labs are about 2.5 inches and the dominate lab about 2inches in length. The dominate lab relentlessly chases the larger 2 labs all day until they take haven in the upper corners of the tank. They spend most of the day in hiding.The tank is well rocked but it appears the dominate lab travel from cave to cave looking for them and then the chase is on. We have tried changing the rocks but it only works for about a day.We originally thought this situation would be temporary and the other fish would take a stand and fight back. The 2 labs that are being chased are now showing black bars and appear to be stressed, should we take the dominate lab out of the tank or will this situation pass over with time?

Answer
Hi Nate,
  It definitely won't pass.  You might consider adding more rock and structure, even if you already have a lot.  My basic measure of structure is that if you can see the back of the tank from the front, you need more structure.  

-- Ron
  rcoleman@cichlidresearch.com
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