angel fish problem

Question
hey Lynda,  I have 2 angelfish and 1 pleco in a 55 gal tank.  I've had them for a long time.  Lately I noticed my "white" angel biting the "black" one on the tail.  I thought maybe a good waterchange along with altering the layout of the fake plants, etc, offering new hiding places would help. I did this and I thought at first that it helped. But a week later he had a bad night getting his tail chomped on horribly.  The next day I noticed white cottony material at the base of his tail (on the wound) and under his mouth.  He still eats but needs help.  What should I do?  (I know some med are hard on plecos and don't want to harm my large one.)

Answer
Hi TJ,
Angels!  They should be called Devils!  What I think is happening is that you have a male, and a female.  They have tried the nuptial dance, and one was weaker than the other.  They do this before accepting themselves as a couple.  They grab each other by the mouth, and pull waltzing all around the tank, letting go, and going back, until they are sure they are of equal force.  If they are not, the stronger one will attack, and try to kill the weaker one.  This is what I think is happening.  You will have to remove your sick Angel, or the other one will kill her/him.  The stronger one will continue to attack.  The Black Angel should be treated quickly with a good antibiotic.   There are many antibiotics on the market that would help cure this poor  angel fish.  Tetracycline, Maracyn, and Maracyn 2 should be used.   The injuries caused by the white angel have now turned into fungus, and it is eating her alive.  The water she is in should be very clean, no ammonia, and nitrates safe.
If left in the tank with the white one, it will be attacked all the time, so you must remove it.  
I hope the little soul will get well soon.
Lynda