Cichlid aggression

Question
QUESTION: Greetings! I have an Electric Yellow lab (Labidochromis caeruleus) and what I
think is a Kenyi Cichlid (Pseudotropheus lombardoi) in a 30 gallon tank. When
I first purchased the fish they got along fairly well, with the Yellow
ocassionally picking on the Kenyi but nothing serious. However, over time the
Kenyi has become the aggressor, highly aggressive during feeding time and
in general. The Yellow has lost a good bit of his/her back fin and some of the
side fins to nipping, become very timid and hides in a cave or near the
surface behind the heater and filter tubes. His color has changed from a
beutiful bright yellow to a faded pale yellow, he has not grown at nearly the
same rate as the Kenyi and he generally just does not look well. I was
convinced by a friend that it was a fin rot problem, and I treated with a
Melaluca based medication for 7 days with no results. I also raised the temp
to 80 F and reduced feedings to once a day, skipping one day a week. The
Kenyi is now grown much bigger than the Yellow, is very active and eats most
of the food before chasing the Yellow into a cave. He does not seem to be
suffering from any fin rot, spots or anything out of the ordinary. I have tested
the water once a week for ph, nitrites, nitrates and ammonia with normal
results for all. It was suggested by my fish store to try one of two things - a
partition or adding guppy fry to distract the Kenyi. Any suggestions are
appreciated!
ANSWER: I had the worst experience with a Kenyi.  He destroyed the inhabitants of my tank.  Your lab has fin rot because the Kenyi has damaged the fins, which became open to sores.  Suggestions are a good idea, but I'd like to add one more.  Make the tank more complex.  More caves, rocks, everything.  Make it so dense, that it's impossible to chase for very long.  Add a small amount of salt and Melafix to help heal the lab.  I am against guppy fry, only because if they die, they become hard to find, and could create unwanted bacteria in the tank.  The partition would be better.  

Another option is to add more fish.  That way the aggression gets diffused.  Red Zebra cichlids are a great choice.  They aren't uber aggressive, but can hold their own when threatened.  Good luck!

---------- FOLLOW-UP ----------

QUESTION: Thank you for the speedy response to my original question, it was very
helpful. As to your recommendation on adding Red Zebras... how many would
you suggest? How many fish can this 30 gallon tank support? Can you tell me
how long I can use Melafix? The bottle recommends 7 days, should I
discontinue use at 7 days even if I see no improvement? Lastly, it was
recommended by another source that I do daily 25% water changes for a week
as a way to assist healing of a sick fish. Is this advisable to you? Thank you in
advance.

Answer
You could probably keep 3-4 in the a 30 gallon.  It'll help diffuse the aggression of the Kenyi, and makes for a nice color display.  Red Zebras do go well with Yellow Labs, so try those again.  Both are fairly docile fish.  I'd consider trading the Kenyi to your local shop for some of the other two.  

As for the Melafix, use it as the bottle directs, and you'll notice immediate improvement.  I swear to you, that stuff works miracles.  As for the water change, I wouldn't do it with the Melafix.  It'll dilute the mixture.  Water changes do help heal wounds, because it helps avoid infection.  However, make sure you put something like Stress Coat when you do water changes during a healing process.  Stress Coat neutralizes chlorine, and aids in wound regeneration.  Good luck!